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By T. C. Rao

This presentation identifies how mineral (coal included) processing profession should look at the challenges (threats) being faced by mineral industry. Presently, the focus is more on supply and demand on minerals. In addition, the R&D activities in the chain of mine-to-metal are paying more attention (if not only on) the processes being adopted, development of new equipments and modeling and simulation. But the profession is grossly ignoring aspects such as impact of the processes on other resources, of the ways we extract, use and dispose them socio-economically and efficiently. A business model which may encompass all these dimensions are essential for the sustainable development of mineral industry and a possible approach in this direction is presented. To start with, for the sustainable growth and existence, the profession must be aware of the prospective impacts of their activities on critical factors such as ? political (changing government policies), geographical (environment, land, water and habitat), which have major bearing on the survival and growth of the industry. Mineral Processing professionals have to join hands with mining engineers to answer some relevant questions related to the impact of mineral industry on society. Mining can become economically viable only if mineral processing engineers come out with innovative solutions to reduce capital and operating costs. The solutions have to be adoptable and practically feasible so that industry looks at us for directions. In fact, we have to move towards beneficiation of nano particles striving towards zero waste. Some of the gaps in the knowledge of procedures being followed in the design and operation of processing plants are highlighted. Enhancing the knowledge base for solving unexplored possibilities, solutions to evolve sustainable development measures which demands innovation both at academic and practicing levels is the need of the future. Well-structured academic programmes are to be formulated so that the graduates of these programmes can make an effort to look at processes/concepts with a new insight and approach; the profession should excite the young brains with challenges. R&D funding agencies have to have a long-term perspective on mineral processing so that closer interactions between academic institutes, industry and R&D organizations are sustainable and that innovations are at least a few years ahead of needs of future challenges. Keywords: sustainable growth

Sep 1, 2012

By John Starkey

"The development of the 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.Previously, it was deemed prudent to select up to 50 t samples of ore for Semi Autogenous Grinding (SAG) pilot plant tests and a second 5 t sample for metallurgical pilot plant work. The methods outlined in this paper show how the 50 t 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 Sonia Helle, Ursula E. D. Kelm

"From a metallurgical point of view, acid leaching of oxide zone copper ore is considered in the first place in terms of ore grade, whole rock mineralogy, rock granulometry, crushed aggregate size distribution, porosity, permeability and corresponding fluid flow characteristics. Despite exhaustive physicochemical and general mineralogical characterization, drops in copper recovery occur and are often attributed to and “unquantified mineralogical misbehaviour” of the gangue phases. This study establishes an experimental link to monitor and quantify the chemical interaction of chrysocolla, malachite and atacamite with reactive gangue phases.Laboratory-scale sulphuric acid (15%) leaching in small columns is carried out using a synthetic rock composed of 57% quartz, 1% ore phase, and 42% reactive gangue. Gangue phases were selected to represent mineralogy found in argillic, advanced argillic, and propylitic alteration zones. Exotic copper ores of Codelco Norte (in particular Mina Sur) served as model for the modal distribution of mineral phases. Natural reactive gangue phases (<200 Tyler mesh) were chosen as pure as possible: Saz-1 and Swy-1 montmorillonites, KGa-1B and KGa-2 kaolinites (all Clay Mineral Society, USA, Source Clays) Nau-2 nontronite, Imt-1 illite (both Clay Mineral Society Special Clays) and Chilean mordenite, laumontite and bentonite. Ore phases are: mineraloid chrysocolla from Radomiro Tomic (Codelco Norte), reagent grade malachite and a purpose synthesized atacamite-paratacamite mixture. Complete chemical, physicochemical and mineralogical characterizations were carried out for ore and gangue phases.The following observations hold for samples with and without mineralization: Smectite-rich gangue increased up to 75% in volume. Once wet, air-filled vesicles formed due to the rapid sealing effect of overlying smectite in the column. No volume change occurred for illite, mordenite and kaolinite gangues. For kaolinite mixtures acid puddles formed on top of the column during initial leaching due to the delamination and barrier formation of this phyllosilicate. Fluid recovery was <60% for expandable phases and reached up to 80% for non-expandable mixtures. These observations confirm the very low extractions obtained in ore with a combined smectite – kaolinite gangue for Mina Sur. The most important mineralogical changes observed in the solid residues are: reduction of basal smectite phase reflections (XRD), and slight loss of illite intensities. This is also reflected in the major element composition of the residues, which demonstrate a loss of Mg, Mn, Ca, Na, K followed by Fe, Al and Si; with their proportions depending on the starting materials. Furthermore, alunogen and meta-alunogen formed, with related phases coquimbite (illite) and godichite (nontronite) also depending on gangue mineral chemistry. For laumontite samples, meta-alunogen and alunogen precipitated from the leachate."

Jan 1, 2003

By C. H. Veloso

"Starch is the most widely used depressant in the reverse cationic flotation of iron ores. There is however, an indication from recent studies, that other polysaccharides may successfully replace them. When starches are used in the flotation of iron ores in the presence of quartz as gangue mineral, their strong adsorption on the surface of iron oxides can be explained by the molecular conformation between the available sites on the mineral surface and two hydroxyls of starches. However, when the gangue minerals are iron-bearing silicates, the strong interaction with starch can occur on these minerals since they have the same surface behaviour as iron oxide. In this work bench scale tests were conducted in order to generate scientific knowledge about other alternatives depressants for the flotation of iron ores. A magnetic pre-concentrate from a skarn iron ore processing plant was used as feed material for flotation tests. The reverse flotation approach was used to upgrade the iron content by removing complex ironbearing silicates. The depressants used in this study were: corn starch, dextrin, carboxymethyl cellulose (CMC) and humic acid. The tests were performed under different pH conditions in order to try to relate the efficiency of depression to the pH used during flotation. The results show the important role of pH as each depressant reached its best performance at different pH values. At alkaline pH the corn starch showed best depression performance while the humic acid is more efficient at pH close to neutrality.INTRODUCTIONIron corresponds to approximately 6% of earth’s crust composition (McDonough and Sun, 1995). It is the most used metal in our lives, some of its properties as resistance and facility to be shaped makes is replacement very difficult. The primary sources of iron on our planet are minerals. The iron-bearing minerals most commonly found in nature and economically exploited are magnetite [Fe3O4], hematite [Fe2O3], goethite [FeO(OH)] and siderite [FeCO3] (L O Filippov et al., 2014). These minerals are commonly associated with other minerals (most of the time not economically exploited) forming the so-called iron ore. Iron ore is the source of primary iron for the world’s iron and steel industries."

Jan 1, 2018

By X. L. Song

A large amount of tailings in concentrators bring a series of problems to the environment and society. It is significant to reclaim the huge tailings and reuse them in industries in order to utilize mineral resources adequately. Primarily Lead-Zinc tailings with a certain quality of clay and feldspar were used to produce ceramic tiles by sintering method under specific technical conditions. By testing the properties of the ceramic tiles, it was shown that the amount of Lead-Zinc tailing used in the tiles was 60%~70%, and the mechanics properties were good. The optimum proportion parameters were Lead-Zinc tailing 60%, clay 35%, feldspar 5%, and the maximum flexural strength of tiles was up to 38.2MPa when it was sintered at 1090? for 30min. Its flexural strength, water absorption and thermal shock resistance reached the State Standard of GB/T4100.4. The product is suitable to be used in pavements and paths of parks.

Jan 1, 2014

By A. Y. Senchenko, Y. V. Kulikov

"The most common technique for selection of grinding equipment is the Bond method implying determination of a ball mill work index (BWi). The method is perfect for greenfield projects where a ball mill must be sized to grind an ore to 80% passing 75-100 µm. Finer grinding will require application of specific correction factors to a standard equation since initially the method was not designated for sizing of fine (minus 75 µm) grinding mills. Significant issues are related to selection of grinding equipment for treatment of originally fine materials when the standard procedure is not applicable. In 1984, Levin published his special technique titled as “A proposed test for the determination of the grindability of fine materials”, where he offered to use the standard Bond ball mill for determination of a specific grinding energy. However, this method did not meet with wide recognition. In 2017, Institute TOMS under guidance of JKMRC’s specialists performed a testwork aimed at verification of a new universal technique for determination of grindability of initially fine materials. An object was to test three aged tailings samples for the subsequent modelling of comminution circuit and evaluation of potential throughput of the existing ball mills with final grind size of ?80 passing 53 µm. In parallel with development of the universal approach, TOMS’ specialists carried out tests according to the Levin method in order to compare the data resulted from two methods. The results from lab ball mill testing on three products following the alternative test methods are presented in this paper along with the testing methodology and results analysis. Specific energy was calculated for regrinding of the materials to the required size. Difference of the examined methods and assessment of their applicability for sizing of full-scale equipment are explored."

Jan 1, 2018

By Daniela Campos, Aldo Casali, Gonzalo Montes-Atenas

The understanding of the effect of the major variables influencing the froth flotation performance may allow both to predict and to identify best operating conditions towards optimizing the process efficiency. The aim of this research work is to model the effect of dissolved oxygen onto froth flotation performance. Experimental pilot plant results were obtained from a continuous circuit consisting of a ball mill and a rougher bank of four flotation cells. A series of flotation experiments were run with different conditions of dissolved oxygen keeping constant most of other operating conditions. Variables difficult to control were measured or estimated. A set of mathematical models suggested in the published literature were tested. It was found that the copper recovery results were highly sensitive to the concentration of dissolved oxygen. The latter confirmed the reactions mechanisms associated to the collecting capabilities of current flotation reagents used in the flotation of copper sulfide ores. On the contrary, the results of molybdenum recovery varied non-linearly with changes in dissolved oxygen which could not be explained directly in terms of the computed specific rate constants. The error analysis confirmed that Klimpel continuous model exhibited the best specific rate constant correlation with molybdenum recovery data. Lastly, the classic particle force balance equations indicated that the adjustments of estimated mineral liberation with experimental data exhibited a turning point when passing from highly liberated to low liberated particles. The values of recovery for such turning point correlated well with the concentration of dissolved oxygen. The results indicated corrections due to changes in the dissolved oxygen must be incorporated in future froth flotation descriptions.

Jan 1, 2014

By Olga D. Khmelnitskaya

The paper presents the results of research on the development of gold recovery technology from oxidized gold-copper ore of one of deposits in Russian Federation. Gold and copper grades in the ore are 9.5 g/t and 0.4%, respectively. Various options of flowsheets, such as direct cyanidation, thiourea leaching, flotation and gravity concentration followed by subsequent cyanidation of con-centration products, were tested. It was established that gravity-cyanidation technology with filtra-tion leaching tails and the use of solutions in the recirculation is the optimal option for ore treatment. The proposed flowsheet provides gold recovery for 91.0% at NaCN consumption 2.5 kg/t ac-cording to the results of pilot testing. Ammonia-cyanide gold leaching was also examined. In comparison with cyanidation, gold leaching solution in system NaCN-NH4OH-(NH4)2CO3 allows NaCN consumption to be reduced three times from 4.5 kg to 1.5 kg per 1 ton of the ore and provides the same gold recovery. Based on the laboratory and pilot plant tests results of gravity-cyanidation technology of gold dissolution, process design criteria were developed.

Jan 1, 2014

By I. Yu. Rasskazov, A. V. Rasskazova, N. M. Litvinova, N. A. Lavrik, V. G. Kryukov

The possibility of the intensification of the gravity processing of complex iron-manganese ore, which contains the finely dispersed inclusions of gold and platinum is shown. Clear mineral fractions of precious metals were sorted out of the different types of ores (quartz-braunite and carbonate- magnetite ore, ferruginous quartzite, carbon-containing shale, breccia-limestone and dolomite breccia). Composition and structures of precious-metals particles was detailed. The industrial content of platinum and gold was found. Precious-metals mineralization is character for all types of ores. High content of platinum is indicated in the carbonate-magnetite (up to 11.3 mg/kg) and quartz –braunite (up to 10 mg/kg) types of ore. Gold is presented in the ferruginous quartzite (up to 1.29 mg/kg) according to the data of the reduced mineralogical analysis. The composition of native platinum depends on the type of the ores: 1) quartz-braunite type contains isoferroplatinum (Pt3Fe) with Cu, Rh, Ir, Ru; 2) carbonate-magnetite type contains isoferroplatinum with Cu, Sn, Ni, Rh, Ir, Os; 3) pyritic-carbon ore contains isoferroplatinum with Sn, Ni; 4) ferruginous quartzite contains isoferroplatinum without admixtures. The ultrasonic treatment of mineral aggregates (P = 41.5 Watt, I = 15 W/cm2) made possible the liberation of fine particles of precious metals. Smooth-shaped or crystalline mineral aggregates are effectively liberated after acoustic treatment. Their surface is freed from impurities. The aggregates with the complex form and structure, which consist of the numerous plates and the grains, are not effectively liberated from impurities. It is shown that the ultrasonic treatment of aggregates with the fine inclusions of precious metals contributes to the liberation of the particles of platinum and gold and intensification of the gravity processing of refractory ore. This approach contributes the increase of the raw-material base of precious metals.

Jan 1, 2018

By S. Banisi, E. Arghavani, M. Pourkani, M. J. Rajabi, Gh. A. Mohamadian, H. Bidshahri, Gh. A. Parsapour

The Sarcheshmeh copper complex flotation circuit of plant No.1 consists of two identical north and south sections where each includes four rougher (each bank consists of 14 cells), two cleaners (each bank consists of 8 cells), two recleaners (each bank consists of 2 cells), and two scavenger banks (each bank consists of 10 cells). The reduction of feed grade along with a change in the mineralogical composition is the main reason of current lower concentrate grade (24%) compared with the design concentrate grade (32%). Because of a lower feed grade, the amount of rougher concentrate has decreased which in turn has significantly reduced the feed rate to the cleaner, recleaner, and scavenger banks. This has increased the mean residence time of the material in the cleaner section resulting in a lower final concentrate grade. A laboratory study showed that the final concentrate grade can be increased by 2-4% if one cleaner stage is added to the flotation circuit. In this research, based on the laboratory results, one cleaning stage was added to the current flotation circuit. In order to make this modification instrumentally possible in the plant, the final concentrate was gravity transported to the Mo-Cu thickeners. This released 2 pumps and associated tanks which made addition of one cleaning stage practicable. Finally, a part of the cleaner and scavenger cells were used as the third cleaning stage. This decreased the residence time in the cleaner and scavenger banks. After implementation of one cleaning stage in the south section of the plant, the performance of the circuit compared with the identical north section. It was found that at the same recovery, the concentrate grade of the south section increased by 2.5%. The promising results led to the implementation of adding one cleaning stage in all sections of the flotation circuit.

Jan 1, 2018

By Kazimierz Trybalski

"Simulation methods have a big potential in the studies and analyses of complex technological processes and schemes. The simulation method used jointly with flow diagrams and related transmittance models allows describing and analysing dynamic characteristics.The paper presents results of simulation analysis of dynamic characteristics of ore dressing system, called closed circuit mill-classifier-mill. Such systems are widely used in ore processing plants. The system was analysed as a typical system with material feedback, to establish its dynamic characteristics.Flow diagram conforming to the technological scheme is presented in a figure. Transmittances shown in the scheme are defined as follows:GMP - transmittance of rod mill,GP, KZ, GW, KZ - transmittances of overflow and underflow streams of spiral classifier, respectively,GMK - transmittance of ball mill,GT - transmittance of underflow stream from classifier to ball mill,GU, MP, GU, MK - fraction transmittance of outflow streams of rod and ball mill, respectively, summed up at classifier input.Taking into account, in base of carried out analysis the transmittance forms of individual system elements. The calculations are based on numeral forms of transmittances of individual blocks, defined through industrial experimentation.Step input function to rod mill was assumed to be a step of mass ore flow rate to the mill. Responses are defined as product densities.This figure demonstrates the way of input signal transmission by consecutive elements of the system and shape of these elements' responses. It can be noticed that step signal undergoes gradual change from the stream of the first order to those of higher and higher orders as a distance from process leading edge increases. Simultaneously, the impulse signal is subject to systematic smoothing and decay. From the technological point of view, the most important is response stream in point 5 (on the above figure) that characterises classifier overflow, which is a final product of this system."

Jan 1, 2003

By Paula Olea, Gonzalo Montes-Atenas

Froth flotation operation is a large tonnage process aiming at selectively separate economically valuable minerals from gangue material. The wellbeing of an industrial froth flotation operation has been historically assessed and understood in terms of many variables known to somehow affect the process performance. Among these variables, air dispersion have been pointed out as key to secure the correct transport of hydrophobic particles to the froth phase and, then, to the concentrate. One of the classic parameters assessed when evaluating the air dispersion in flotation tanks is the superficial gas velocity. Many reports have focused on studying the superficial air velocity profiles across the pulp phase and theories have been based on the fact that the measurements should be performed in the so called "quiescent zone", which is a volumetric region inside a flotation cell of difficult determination. The hypothesis behind this research work is that the reporting of particles to the concentrate would provide a better correlation with the effective air flowrate pattern created in the froth phase. The aim of this study, as a first step towards developing a flotation model fully froth phase-based, is to estimate the effective surface area used in a flotation cell derived from results obtained with a specific setup at laboratory scale. The methodology considers running a thin lateral flotation cell cut at different superficial air velocities, with and without particles. It was found a non-linear correlation between the superficial air flow rate and the characteristic distance between the vertical wall next to the cell lip and the cut point where the foam or froth flowrate almost stops contributing marginally to the overall amount of solid particles transferred to the concentrate. The presence of hydrophobic particles reduced the mobility of the froth phase reducing the characteristic distance.

Jan 1, 2014

By Cesar Gomez, Jaime Álvarez, Lisette Wen

Laboratory mechanical flotation cells are extensively used in mineral processing for running batch flotation tests with a variety of purposes, for example assessing feed characteristics, determining flotation kinetics, or testing of new reagents and procedures. It is known that the results obtained depend on the operation mode, self-aerated or forced-air, and on the operating conditions selected for the test, in particular impeller speed and gas flow rate. These different results are a consequence of changes in size distribution of the generated bubble population and its remarkable evolution when frother is added; variations in bubble size affect the bubble surface area flux (BSAF), a variable which correlates with particle collection. Results of a two-phase (air-water) test program designed to measure bubble size for a variety of combinations of impeller type and speed, gas flow rate, frother type and concentration, and cell volume, demonstrated the wide range of BSAF with which the cell can be operated. The results obtained in this work demonstrated that gas dispersion in a forced-air lab flotation machine is significantly affected by the characteristics of the impeller/cell geometry combination in use, and the operating conditions selected. Operating conditions must be carefully selected and maintained during the test to ensure consistent results, in particular when frother concentrations below 20 ppm are used, because frother concentration in the cell will decrease as flotation progresses as a consequence of frother partitioning to the concentrate.

Jan 1, 2014

By X. Tong

Flotation researches of indium-beard marmatite from the Dulong multi-metallic ore in the Yunnan Province of China has been studied in order to improve the grades and recoveries of zinc and indium of the zinc concentrate in the Dulong concentration plant. The experimental results have shown that copper sulfate mixed with a chemical reagent X-1 as the activator in the marmatite flotation produced a much better beneficiation than copper sulfate alone, increasing the zinc and indium recoveries of 10% and 6%, respectively, while the concentrate grades were unchanged. Also, the new activator acted well around pH 10, allowing large savings on lime consumption in the marmatite flotation. In addition, it has been found that a sufficient activated time of activator with ore slur-ry in the flotation is needed to achieve good beneficiation of the marmatite ore.

Jan 1, 2014

By Marzio Piller, Girolamo Belardi, Jure Mencinger, Paolo Bozano, Gianni Schena

"The hydrodynamics of the Tri-Flo™, a two stage cylindrical cyclone used in dense media separation, is studied using Computational Fluid Dynamics. The flow field is simulated with an Euler-Euler Volume of Fluid two-phase approach and the Reynolds stress turbulence model.A unique feature of the device is that the separation medium suspension is pumped and introduced tangentially into the two cylindrical compartments while the raw feed is conveyed to the feed hopper and fed at the axial inlet. This feature allows to use less pumping energy and limits the unavoidable production of fines. The Tri-Flo™ complex flow pattern is little known but central to the efficiency of the separation.The velocity field is computed within the two compartments of the separator. The interface of the air-core that forms in the inner axial part of the cylindrical sections is identified and visualized. The numerical results for a reduced-size 100 mm ID Tri-Flo™ are compared against laser Doppler measurements on a transparent acrylic model (Chinè, 1995) operated with water. The robustness of the model and its prediction capability are verified.The possibility to accurately predict the velocity profiles within the vessel and their dependence on the main Tri-Flo™ operating and geometrical variables paves the way to a better understanding of the functioning of the separator, its design improvements and scale-up."

Jan 1, 2014

By A. D. Bas

Copper minerals present difficulties during the cyanide leaching of gold ores leading to excessively high consumption of cyanide (and oxygen) coupled with low extraction of gold. Copper cyanide species, if present at high levels, adversely affects the downstream processes such as the activated carbon adsorption and the effluent treatment. In this study, the extraction of gold from a copper-bearing gold ore by ammoniacal cyanide leaching was studied. Furthermore, ammonia leaching as a pretreatment process ahead of cyanide leaching was also examined. Only ~12% of gold was extracted by direct cyanide leaching of the ore. The addition of lead nitrate did not affect the leaching of gold. When ammoniacal cyanide leaching system was used, the extraction of gold was significantly improved to >90%. Similarly, the pretreatment of the ore by ammonia leaching was shown to lead to high gold extractions (98%), in subsequent cyanide leaching with significant reductions in the consumption of cyanide. This appeared to be linked with the ready dissolution/removal of copper during ammonia leaching.

Sep 1, 2012

By André Mans, Frans B. Waanders

"Ferrosilicon (Fe-Si) is an important commercial material and it forms the basis of the powder used in dense medium separation (DMS) of various minerals in a minerals beneficiation process. Current losses of Ferrosilicon (Fe-Si), which is used in the dense medium separation (DMS) of iron ore at Kumba Resources, Sishen, South Africa occur due to adhesion to the separation products and also by being present in the effluent stream, due to abrasion. The losses contribute greatly to the running cost of the plant and the purpose of this project was to determine the characteristics of the unused Fe-Si and then to characterise the changes that occur during storage and the use thereof.A Scanning Electron Microscope (SEM) and Mössbauer Spectroscopy (MS) were used to investigate the characteristics of the fresh and used Fe-Si. The SEM analyses of the Fe-Si yielded a composition of 15 wt.% Si and 85 wt.% Fe with minor impurities of Mn and Cr (<1 wt. %), resulting in an ordered phase with a calculated composition of Fe2Si. The average density of the Fe-Si was found to be 7.177 g.cm-3 whilst the size distribution was determined with the d50 of the particles being approximately 30 µm. A slurry, containing 10% solids was prepared, which had a density of about 1.1 g.cm-3 and this slurry was used to conduct the various experiments under laboratory conditions at the university. Samples were taken at regular intervals from a storage container containing a lime solution as well as from a closed circulation circuit system, kept at a constant temperature of about 60°C. Mössbauer Spectroscopy yielded, for the new fresh Fe-Si-samples, a two-sextet spectrum with hyperfine magnetic field strengths of 19.9T and 30.7T respectively, and the yellow-brown froth was found to be akaganeite or ß-FeOOH.It was found that the biggest loss of Fe-Si was due to the abrasion of the particles during the DMS process. A possible change in magnetic properties was also observed, leading to further losses that could occur during prolonged use of the medium. No clear changes to the Fe-Si occurred during correct storage methods, as was initially thought."

Jan 1, 2003

By Paulo Castillo, Cesar Gomez, Jaime Alvarez

Operations using flotation to produce mineral concentrates require testing of frothers to characterize their ability to preserve bubble formation size and to build a stable froth. Many techniques have been proposed to measure parameters associated with these two roles. These techniques focus, in general, on only one of these roles and are based on special equipment operated at conditions quite different from those existing in industrial cells and columns. Both roles have been simultaneously characterized in a laboratory flotation column, but the requirements associated with the installation and operation of one of these units, are a serious limitation for its use on-site. A technique based on the use of a laboratory mechanical cell, a common piece of equipment in operations, will have wider application. Establishing the ability of a frother to control coalescence by preserving bubble formation size is done through bubble size measurements as a function of frother concentration. Froth build-up and stabilization is associated with the amount of water carried by bubbles into the froth layer, which has been demonstrated to correlate with the gas holdup in the collection zone. Procedures devised for determining the critical coalescence concentration (CCC) from measurements of bubble size as a function of frother concentration, and the gas holdup by collection of water displaced from the cell by the presence of bubbles at different frother concentrations, were tested. Three analytical-grade frothers were utilized: a straight-chain (1-heptanol) and a branched (MIBC) alcohol and a polyglycol (PPG425). The results obtained at a standard set of conditions, demonstrated consistent differences between these frothers, and the ranking from least to most effective for reducing bubble size or decreasing water drainage followed the same sequences found when more complex frother characterization techniques are used.

Jan 1, 2014

By Pengbo Chu, James Finch

Bubbles around 1 mm diameter provide the high interfacial area for capture and transport of hydrophobic particles in flotation. The formation of such fine bubbles is commonly achieved by addition of frothers that appear to simultaneously retard coalescence and promote break-up. High inorganic salt content in process water can substitute for frother. In this work we focus on the action of salt (sodium chloride) on formation of bubbles by break-up. An experimental setup that isolates break-up from coalescence was employed. A pocket of air is exposed to controlled mechanical turbulence to produce single bubbles by the induced deformation of the air and the events imaged. The presence of salt is shown to produce smaller bubbles than in water alone. Comparison with a similar study on frothers is made. The argument is advanced that the presence of frother and salt creates surface tension gradients at the air/water interface which add to the mechanical energy of the deformation and break-up process.

Jan 1, 2014

By John A. Herbst, Ming Song, Xiangjun Qiu

"It has been known for sometime that as wear occurs in tumbling mills there is an associated change in mill throughput. These changes have traditionally been simplistically, attributed to “mill volume effects”. New high fidelity simulation (HFS) tools (involving DEM, CFD and Breakage models) are now giving new “microscale” insights into the complex interactions that occur between evolving lifter/liner profiles and breakage. An illustration of this analysis is shown in Figure 1 below.Here we see that after a new lining is installed (Region I) the wearing process reduces the liner thickness resulting in a larger power draw and an associated higher throughput until Region II is reached. By this point the lifter height is reduced significantly changing charge motion (less cataracting) the power begins to decline, but the comminution efficiency increases with this type of “calmer” breakage environment therefore the throughput continues to increase. In Region III the lifter is no longer providing the minimum required charge lifting action, the power and the throughput both drop off significantly. In the last two stages the behavior is especially complex because throughput is not linearly related to power since grinding efficiency is changing.The study described here shows that these new HFS tools allow the design of wear part profiles which will maximize mill productivity over the entire life of liner/lifter systems. A simple example of such a design procedure is shown involving the selection of a sinusoidal profile for a 34 ft diameter SAG mill.The paper discusses how the principles exposed in this simple example can be applied to search for an optimal profile in which non-standard modifications are allowed to compensate for throughput or wear shortcomings of standard profiles."

Jan 1, 2003