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By F. Bello, R. Yanez, M. Pinto, T. Errazuriz

"Throughout its operation, Minera Esperanza (ME) will deposit one of the largest tonnages rates of high density tailings in the world with a solids concentration of close to 67% by weight. The tailings presently being deposited have a solids concentration of approximately 62% - 64%, and so cannot be used to directly characterize the flow and deposition characteristics of the higher concentration tailings. To increase the knowledge of the behaviour of their tailings, ME, with the support of Golder Associates, developed a large scale tailings deposition test with a capacity of 30,000 tonnes per day (1,200 m3/h). The test was carried out by depositing tailings into two large cells or paddocks in five stages. Multiple spigots were used to allow different flows to be deposited. At each stage, topographical surveys of the natural terrain and the geometry of the deposited tailings, as well as continuous flow measurement and periodical rheological characterization of the discharged tailings were conducted to create a data set against which beach slope models could be calibrated and then used to predict performance of the higher concentration tailings under different deposition scenarios. This study adopted the beach slope prediction model proposed by A.L. Li (Li, 2011). The model was successfully adjusted to the observations made during this large scale field test by applying the values measured in-situ. This paper presents the application of the model, the results obtained, the findings, and the analysis of possible future scenarios. The model was applied, using the discharge flow rate, the geometrical characteristics of the discharge area, and the rheology with its variation along the beach to estimate the development of the beach formation and the steady state of the beach slopes. Through the use of dimensionless variables, the model was applied to higher solids concentration scenarios, obtaining results that would allow beach slope estimation at different deposition stages in multiple scenarios of varying parameters such as flow, rheology and geometry of discharge area."

Jan 1, 2014

By Y. M. Zhu

Lead in environment often causes a serious health hazard. The removal of Pb2+ from aqueous phase is a beneficial project. In this paper, deposited Saccharomyces cerevisiae (S.c.) was chosen as adsorbent, Pb2+ ions as adsorbate, and the process of biosorption was studied. The dynamics of the adsorption was investigated. The adsorption mechanism of Pb2+ by S.c. cells was also investigated by detecting microstructure, zeta potential under different pH value, FT-IR spectra of the S.c. particles before and after biosorption. It was shown that the biosorption of Pb2+ by deposited S. c. is a rapid process, and the adsorbing equilibrium is reached within 10 minutes. The Zero point of zeta potential of S.c. cells is pH=3.3. When 2.0<pH<3.3, there exists biosorption (biosorption rate 76%~88%), which means static bio-sorption been not the only kind of biosorption. FT-IR spectrum analysis showed that groups on bacteria surface were mainly characteristic groups of protein and amylase; oxo-groups and nitric-groups on S.c. cell surface could chelate with heavy metal ions. Chemical adsorption might exist in the process.

Jan 1, 2014

By Paulo Sérgio de Oliveira, Joaquim D. Donda, Andreia C. Rosa

"The search for energy efficient technologies for comminution processes is constant in mineral processing studies, since those processes represent a major percentage of operational costs. In this context the use of stirred mills is increasing, especially for ultrafine grinding. Although many authors claim that these new equipment are more efficient than the conventional ball mills, there were very little chances to prove that in a practical way, since there are few industrial circuits where those technologies perform the same duty. Therefore, the regrinding circuit of Germano second concentrator offers an interesting opportunity: a vertical mill operating in parallel with two ball mills. During almost two years of operation, several sampling campaigns were conducted to evaluate the vertical mill performance and to compare the operational data of the three mills. The industrial data was also compared to jar mill tests results, which are monthly conducted in Samarco labs in order to predict the specific energy consumption required by the ore fed to these circuits. The vertical mill demonstrated the same ability to achieve the product specifications of the ball mills while proved to be able to reduce the medium specific energy consumption in about 40%."

Jan 1, 2014

By Crasta Jeason, T. Sreenivas, M. Narasimha

The subtle nature of the flow inside the hydrocyclone has encouraged development of mathematical models for predicting its performance, which are widely used in simulation of comminution circuits. But most of the models available are based on single average feed density. But the feed to hydrocyclone classifier is generally mixture of particles of different densities. This effect of varying density of feed particles on performance of hydrocyclone has been reported in literature. Further investigation of the effect of multi component feed on the performance of hydrocyclone is the objective of this work. This work involves experimental work to study multicomponent behaviour in various size cyclones. The performance of hydrocyclone for feed mixture of magnetite and quartz has been studied. The effect of presence of magnetite, a high density material on efficiency of separation of quartz has been analysed. It was observed that the effect of component interaction increases with feed solids concentration leading to an increased cut-size for a given optimum cyclone conditions. Based on the multi-component exiperiments available in literature, a concept for modeling the performance of hydrocyclones is proposed. A set of semi-empirical model equations for cut-size, sharpness of separation are presented. An attempt to validate the new hydrocyclone model on multi-component behaviour is made.

Jan 1, 2014

By Anuttam Patra, Romain Bordes, Andreas Fredriksson, Tommy Karlkvist, Krister Holmberg, Kota Hanumantha Rao

The present investigation aims to develop and distinguish mineral specific reagents with two functional groups for use in flotation of calcium containing minerals. For this purpose, a series of dicarboxylate-based surfactants with varying length between the carboxylate groups (one, two or three methylene groups) were synthesized. As reference, a surfactant with the same alkyl chain length but with only one carboxylate group in the polar part was synthesized. The adsorption behavior of these new reagents on pure apatite and calcite mineral surfaces was studied using Hallimond tube flotation, FTIR and ? potential measurements. The relation between the adsorption behavior of a given surfactant on a specific mineral surface and its molecular structure over a range of concentration and pH values, as well as the region of maximum recovery were established. It was found that one of the reagents, with a specific distance between the carboxylate groups, was much more selective for a particular mineral surface than the other homologues synthesized. This selective adsorption of a given surfactant to a particular mineral surface relative to other mineral surfaces as evidenced in flotation studies is substantiated by ? potential and infra-red spectroscopy data.

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 Anatoly F. Usov, Vyacheslav A. Tsukerman

"The Russian scientists have developed a new energy saving method for an efficient destruction of the sturdy and hard materials (rocks, ores, frozen soils, concrete blocks ets.) - the Electric Pulse Discharge method of materials destruction (EPD). The detailed researches of a broad circle of problems connected to development EPD-disintegration of materials of a various nature and area of use are executed. The electrical and power characteristics of process, physical fundamentals of selectivity of a breakdown and destruction are investigated, the means of electric pulse splitting and refinements of materials are developed, the technological efficiency of disintegration of industrial minerals estimated.One of the most important characteristics of the EPD-disintegration of ores is the high selectivity of destruction, which provides a large ratio of useful minerals' grains opening, and at the same time, it destroy them less. This ensures in the subsequent stages of beneficiation of ores considerable increase of the extraction and improving the quality of concentrates.The technological tests of various industrial minerals have shown a possibility the EPD-disintegration, as a process that provides the best efficiency of disclosure of useful minerals in all types of ores. Technological and economic efficiency of the method of ore beneficiation is the highest for difficult beneficiated ores with rather low extraction by existing methods. The increase of extraction in this case can reach several percents. As a rule, at a EPD-disintegration the disclosure of mineral grains happens in earlier stages of material comminution than at a mechanical comminution, and with less damage of products. This promotes a simplifying the process of ore preparation and for reducing the power consumption."

Jan 1, 2003

By Ming’an Wei, Chuanyao Sun, Zhenguo Song, Zengwen Dou, Yangge Zhu

"The effects of pH value and dissolved oxygen(DO) in the pulp to the Eh and flotation recovery of pyrite were investigated using potential online detection system. The effects of DO on the Eh and flotation recovery were tested which DO changed from 0.5mg/L to 19.5mg/L in six different pH buffer flotation systems (pH: 4.00, 5.62, 6.86, 9.18, 10.01 and 10.96 respectively). Results of potential detected online demonstrated that the pyrite electrode has nearly the same response to potential as with platinum electrode for the FeS2-xanthate-H2O flotation system under the study conditions. Pulp potential and recovery of pyrite were remarkably influenced by pH, both of them decreased with the increasing of pH and, especially, sharp decreased after pH above 9. As the concentration of DO was increased, the Eh was also increased in all the six different buffer solution, while the flotation recovery was decreased. And the amplitude of variation for Eh was not obvious in acidic and neutral solutions, but on the contrary, the change for flotation recovery was remarkable in neutral and alkaline conditions. This may indicate that the flotation of pyrite will be deteriorated in alkaline and high DO concentration conditions."

Jan 1, 2014

By Jens Markowski

The EU Directive 2000/53/EC on end-of life vehicles (ELVs) states that in 2015 at least 85 wt.-% of a vehicle has to be reused or recycled. This result in the obligatory need to separate additionally metallic and other components of the automotive shredder residues (ASR), so that they can be professionally prepared for recycling and reuse further. Currently the iron-containing fines of ASR are deposited as it is not possible to process in blast furnaces due to its particle size (< 4 mm), composition and material properties. Additionally problems are also caused in handling and transportation (dust) of the material. This work focuses mainly on the ASR materials utilization in blast furnaces. Material was further separated into two consecutive fractions by carrying out repeated crushing and magnetic separation twice. The two fractions have significantly higher iron content (up to 75 wt.-%) compared to the initial material mixture. The materials were assessed for their usage in blast furnaces based on the possible pelletisation with and without binders, stability of pellets, shape and size of pellets, etc. Pelletisation of the material was carried out with a single mould pellet press. Further lignite coal was added to the mixture as additive which improved the pelletisation behavior and the mechanical stability of pellets. Lignite coal was chosen as a reducing agent in the blast furnace process contributing towards additional savings in energy supplied. The experiments reveal that the production of pellets from iron-containing fines is possible with a lignite coal admixture of about 15 wt.-%. These pellets displayed good mechanical stability and can be used in blast furnace processes in recovery of the recyclable metals which are currently not recycled. The recycling of not yet recyclable metals would reduce the deposition and can be easily adopted into the economic cycle by their utilization. Keywords: Automotive shredder residue (ASR), FE-fines, pelletisation

Sep 1, 2012

By Gregory Harbort, Sarah K. DeBono, Alan J. Monaghan, Emmanual V. Manlapig

"The Jameson Cell is a type of flotation machine in which air and pulp are brought together in a vertical tube called a downcomer. Within the downcomer the air and pulp are dispersed into a dense foam of fine bubbles, which creates a favourable environment for bubble-particle collision and subsequent collection of hydrophobic particles. The intense collection zone within the downcomer can be considered similar to the zone between the rotor and stator in mechanical flotation cells.Research into the bubble-particle collision and fluid dynamics of mechanical cells rotor-stator zone has been limited by the difficulty of achieving accurate measurements in production sized machines. With the Jameson Cell the downcomer is largely external and separated from the flotation tank, allowing ready access to the primary contacting zone for measurement and analysis.An investigation has been undertaken into the operating characteristics of the downcomer relating to bubble-particle collision. An effective mapping of the downcomer has been made through measurements of void fraction and bubble size taken across cross sections of the downcomer. Analysis of these measurements has provided an interpretation of the variations in the air and fluid dynamics, bubble size and distribution throughout the downcomer chamber.Existing models of bubble-particle collision efficiency are reviewed in respect to the collected information and refinements conducted. The area of maximum bubble-particle collision efficiency is defined. Findings are related to operation within the rotor-stator zone of mechanical flotation cells."

Jan 1, 2003

By P. Saha, D. M. Chakrabarti, J. P. Srivastavam, P. Bhattacharyya, B. R. Sarkhel, Banerjeem B.

The phosphatic soil deposit at the Sukulu hills region of Uganda contains 10-12% P2O5. The ore occurs as a naturally degraded soil deposit containing a very sticky slime composed of earthy lateritic minerals. Desliming of the ore, which is imperative for its further beneficiation, is an extremely difficult hurdle to overcome for its commercial utilisation. Earlier studies on samples of the same ore at the National Metallurgical Laboratory (NML) and abroad established that it was necessary to pass the ore through a series of three stages of desliming, each consisting of a step of vigorous attrition scrubbing followed by hydrocycloning, for effective elimination of the sticky slime. In the present paper an innovative use of the very strong shear-fields created inside a hydrocyclone has been discussed, that could effectively eliminate the stubborn slime from the ore. The standard design of the hydrocyclone was suitably modified to increase the shearing effect on the slurry. It was possible, through the application of this modified hydrocyclone, to not only totally eliminate all the stages of attrition scrubbing, but also to reduce the subsequent stages of hydrocycloning. The modified technique yielded a concentrate of grade comparable to that obtained by employing the earlier more complex flow sheet, with about 25% higher P2O5 recovery.

Jan 1, 2003

By Tsvetan Damyanov, Nikolay Hristov, Evgeni Kostadinov, Lubomir Kuzev

"The process of grinding in drum mills is directly dependent on the dynamic forces occuring in the free movement of the grinding bodies in the volume. The subject of discussion are the potential impacts between grinding bodies having different shape and equal weight in a drum mill that has a diameter of 1200 mm. The study utilised ball grinding bodies having a diameter of 120 mm and tetraballpebs having a conditional diameter of 120 mm. The study was carried out using the Solid Works Simulation software. The following cases were examined: • Impact between two identical grinding bodies; • Impact between a grinding body and the shell surface. The study provided numerical values for impact force, kinetic energy of impact, linear speed of impact, linear displacment of the center of gravity and duration of impact deformation. The impact force of the balls is approximately 179000 N. The impact force of the tetraballpebs with typical vertices, edges and spherical surfaces depending on the area of impact is 177000 to 185000 N. Upon impact between two spherical surfaces of tetraballpebs, the contact area is 263.55 mm2, which is more than twice the contact area upon impact between two balls, which is 114.39 mm2. This determines better conditions for the transmission of kinetic energy by reducing opportunities for overgrinding."

Jan 1, 2014

By Vasily V. Lodeischikov, Adolf F. Panchenko, Olga D. Khmelnitskaya, Vladimir E. Dementyev

Pilot plant tests of underground gold leaching from Maminskoye deposit oxide ores at a grade of 0,7 g/t Au were carried out. The underground leaching flow sheet includes Au dissolution by chlorine-containing solutions, Au adsorption from solution on active carbon, carbon concentrate ashing and calcine melting to produce high grade gold concentrate. The underground leaching system throughput was 15 m3 of solution per hour. Gold concentration in pregnant solutions was 0.12-0.13 mg/l. Gold recovery from solutions into carbon was in the range of 63-84%. It was demonstrated that the low Au recovery in the adsorption cycle was due to the presence in pregnant solutions of "active" chlorine, which destroys active carbon and causes a sharp decrease of the carbon loading capacity for gold. To improve the adsorption indices, previously dechlorinated pregnant solutions using bituminous coal or Na2S2O3, is recommended. Ion exchange process was tested as an alternative for gold extraction from dechlorinated solutions. In the testwork period, 4.4 kg of gold were produced with a chlorine consumption of 3.5 kg per 1 g of gold. During the tests a program of environmental protection measures was completed to provide the necessary safety precautions of the underground leaching works.

Jan 1, 2003

By Jiang Wenli, Zhang Yimin

In order to enhance the quality of iron concentrate from magnetic separation, reverse-flotation technology is often applied in an iron ore dressing plant.However, this technology has disadvantages in terms of operating cost,energy consumptionand environmental protection(Zhao, Wu& Wang,2005).Developing innovative equipment to process magnetite ore more-effectively is a way to get rid of these disadvantages of reverse flotation and improve the quality of iron concentrate.This paper describes the development of Complex Flashing-Field Magnetic Cleaner,a new kind of equipment based on the principle of combination of separation in magnetic field and separation in gravity field(Hao & Jiang, 2002).This innovative equipment possesses a tailor-made magnetic system and has the characteristics of a magneticfieldwhich can strengthen the formation of magnetic agglomerations and the dispersion of gangue mineralsto improvethe quality of separation.The automatic control system developed specifically for this equipment can further increase the accuracy of separation and stabilize the process.

Jan 1, 2014

By Manuel Diaz

"In these difficult times for the mining world, mainly due to the global uncertainty about metal prices and the increased activity of opponents to the mining industry, it is essential that mining companies focus on efforts and strategies that will give them the most flexibility to succeed under the fury of these phenomena. The careful management of systems to control costs, and indicators to measure with great precision actual variations in costs and cash flows, are essential to adequately manage the uncertainty. Similarly, clear corporate and regional strategies designed to maximize cash flow and operating margin will allow the company to be better prepared to face any negative situations caused by declining metals prices, stricter government regulations and increasing social pressure. Gold Fields Limited, a corporation of South African origin and with more than 100 years in the gold mining business, has developed the ability to adapt to large changes generated by different global crisis throughout its history. This occasion will be no different. Given the critical situation of the mining industry in the world today, Gold Fields has embarked on a re-structuring plan at global level that will allow much closer control and real efficiency of production costs. This plan includes the creation of regional business units that allow greater independence for each region while still preserving the standards and cultural values of the Corporation. This presentation will explain why we believe that this approach combines the best aspects of the two styles of business, and what are the expected results. In the Americas Region, Gold Fields currently operates Cerro Corona, in Peru. In addition, the company is considering opportunities for growth in Chile, Brazil, Mexico and Canada."

Jan 1, 2014

By S. Nitta

The present study deals with a new approach in calculating the size of Tower Mills. The method is derived from the application of grinding kinetics theory on the analysis of by-gone operational data. It requires only information on the capacity of the mill to be designed, the product fineness and the Bond?s work index to give an accurate and simple prediction of Tower Mill characteristics. An example illustrates the different steps of calculation.

Jan 1, 2014

By M. Gonzalez Fernandez

"Commercially introduced in 2004, the SAGDesign™ test has today proved its efficiency for sizing SAG mills for a wide variety of ores, from very soft to very hard ones. The interest of building a model using the SAGDesign™ test specific energy is the introduction of such a model into a complete process simulator making it possible to predict a complete material balance. The developed model compares the required specific energy with the energy provided by the mill. This energy calculation is derived from the Austin Power Formula. The specific energy provided by the test is corrected, using various parameters, such as the Ball Mill Work Index, to take into account the true operating conditions, the feed and product sizes. The core of this model allows the determination of the product d80 using the mill geometry, its operating conditions and of course the SAGDesign™ test results. To be included in a simulator, the model must also predict the overall size distribution of the SAG mill discharge. Assumptions to answer this point are presented here. The model has been implemented in the USIM PAC simulator. It is used either to predict the product size distribution for a given SAG mill, but also to size a SAG mill for getting a required reduction ratio. INTRODUCTION Over the last few years several types of new comminution machines have been introduced in the market. The most notable newcomer was the HPGR (Morley, 2006). But, even when these machines have some advantages, they have not earned the trust of the mining industry. That is why the established technologies still being the first choice. And, in comminution, that first choice are SAG and ball mills. The design of ball mills has been well understood for a long time. The Bond Ball Mill Work Index is the standard test which helps to describe the ore in terms of energy requirements for milling. Unfortunately, the development of an equivalent test to characterize the ore subject to SAG milling has taken some time. As of today, several tests are available in the market, like the MacPherson test, the MinnovEX SAG Power Index (SPI™), the JK Drop Weight Test, the SMC Test® and the SAGDesign™ test (Verret et al., 2011). The SAGDesign™ test, developed by John Starkey in Canada in the early 2000s (Starkey et al., 2008, 2015), has become one of the standards to assess the grindability of an ore in a SAG mill. One of its advantages is the reduced sample mass needed to perform it, hence, the reduced cost. The second one is that the output of the test is straightforward, it is the energy required to grind the ore between two sizes. Because of this energetic approach, the results provided by the test can be directly applied to size a new mill or to assess the performance of an existing mill."

Jan 1, 2018

By A. Boulton

Low molecular weight synthetic polymers substituted with hydroxyl, carboxyl or sulfonate functional groups were used to improve the flotation separation of zinc or copper sulfide minerals from iron sulfide gangue minerals in three massive sulfide ores of different mineral composition. These polymers produced significant improvements in zinc or copper grades as a result of a selective depression of iron sulfide minerals. These results are significant considering the differences in ore type, proportion and type of iron sulfide minerals present, and grinding medium used in this study.

Jan 1, 2003

By C. Dorfling, P. Albertyn

"Hydrometallurgical recovery of metals from printed circuit board waste typically involves multiple leaching stages; conventionally, base metals dissolution by mineral acids is followed by leaching of gold using cyanide or halide based lixiviants. Alternative lixiviants for gold leaching can reduce the potential hazardous nature of operation. The aim of this study was to investigate the feasibility of using thiosulfate as lixiviant for gold leaching from waste printed circuit boards. Batch leaching tests were performed to investigate the effects of thiosulfate concentration (0.1 – 0.2 M), ammonium concentration (0.2 – 0.4 M), pH (9 – 10.5), solids content (25 – 50 g/L), and copper content of the feed material on the gold leaching behavior. The concentrations of metals in liquid samples were determined by means of inductively coupled plasma atomic emission spectroscopy, and high pressure liquid chromatography was used to evaluate thiosulfate degradation/consumption. The ratio of thiosulfate to ammonia was found to have the most significant effect on the extent of gold leaching, with the best gold extraction observed at a ratio of 0.5 mole thiosulfate per mole ammonia. The lower pH range of 9 – 9.5 generally produced better Au leaching, while low copper extraction during the first stage base metal leaching stages has proven to be detrimental to gold leaching from the residue. Thiosulfate degradation/consumption increased and gold extraction decreased with higher residual copper in the feed. An optimum gold extraction of 78.5 % from base metal leach residue was achieved with 0.2 M thiosulfate, 0.4 M ammonia, and 0.02 M cupric ions at 25°C in the pH range 9 – 9.5.INTRODUCTION Background and Aim The recycling of e-waste is becoming increasingly important as it provides certain economic benefits apart from the obvious environmental benefits. Printed circuit boards (PCBs) are found in most forms of e-waste and contain especially high concentrations of base and precious metals. Hydrometallurgical processes are often considered for the recovery of valuable metals from PCBs; these processes normally implement several leaching stages to selectively recover certain metals."

Jan 1, 2018

By Andrew T. McBride, Malcolm S. Powell, Indresan Govender

"Current empirical Semi Autogneous Grinding (SAG) mill models contain assumptions concerning the amount of energy available for particle breakage, how this energy is distributed in the mill media and the rate at which the energy is transferred. Despite these assumptions the JK SAG model is highly functional with a proven track record. DEM provides a numerical framework to greatly improve on these assumptions that were necessary due to a lack of available input data.This paper identifies key outputs of the Discrete Element Method (DEM), such as energy spectra and impact probability distribution. It describes how they can be incorporated into current mill models utilising practical rock breakage data. The rate at which energy is transferred is shown to be dependent on particle position and mill rotational speed and not once per cycle as previously assumed. Based upon this an improved energy transfer methodology is presented. The fundamental outputs of the DEM are validated against experimental three-dimensional particle tracking data, so as to establish whether the DEM produces correct energy transfer predictions on the inter-particle level, which is crucial to this work. • Effective Experimental ValidationAn automated 3D tracking technique is employed to study the motion of plastic particles deep within the charge of a 142mm diameter experimental mill. A Biplanar Angioscope is used to film the mill with X-rays in two planes simultaneously at 50 frames/s, with a shutter speed of 1/3000s. A marked ball within the charge is tracked for over 2 minutes and the resulting digital images processed by a fully automated imaging technique, which locates the 3D coordinates of the particles to within 0.2mm. With over 250 circulations, this provides statistically rigorous and accurate data for verification in the numerical modelling of mills.A series of validation techniques have been developed to compare the experimental trajectory data with the outputs of both 2D and 3D DEM simulations. The techniques describe the shape of the charge and the particle motion within mill, allowing objective comparisons to be made of key features of the charge, such as the equilibrium surface and the centre-of-circulation."

Jan 1, 2003