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By D. Govender

Theoretical flotation models suggest that there is a positive relationship between bubble-particle collision rates and turbulent kinetic energy dissipation. Fine particle flotation performance is generally enhanced by increased collision frequency and hence higher energy dissipation. Contrarily, increased turbulence in the rotor-stator region is related to higher detachment frequency of the coarser size range. Therefore, the optimal modes of recovery for the ?fine? and ?coarse? size classes are diametrically opposed. Industrial applications have previously confirmed that applying greater power to flotation slurries yields significant improvements in fine particle recovery. However, recovery of the coarser size class favors a different flotation environment. An improvement in the kinetics of the fine and coarse size classes, provided there is no adverse metallurgical influence on the intermediate size ranges, is obviously beneficial to the overall recovery response. Managing the local turbulent kinetic energy dissipation, and hence the power imparted to the slurry, offers the benefit of targeting the particle size ranges exhibiting slower kinetics. FLSmidth recently introduced the practical implementation of this concept. In principle, it decouples flotation regimes where fine and coarse particles exhibit preferential recovery. In the case of naturally aspirated machines (Wemco®), it is referred to as Hybrid Energy Flotation? and incorporates at least three phases: ? Standard flotation machines (standard energy input, rpm, rotor size/type) at the beginning of the row, where flotation is typically froth phase limited and operational, and set-up parameters have a limited influence on the recovery. ? Higher-powered flotation machines (high rpm, high power rotor size/type) at the end of the row to improve fine particle recovery. ? Lower-powered flotation machines (low rpm, low power rotor size/type) to enhance coarse particle recovery. In evaluating the effect of turbulent kinetic energy on flotation performance, the spatial distribution and its effect on size denominated recovery needs to be evaluated. The mean energy dissipation rate is a measure of the bulk energy input, but CFD-based models offer a more introspective view of flotation sub-processes. A CFD-based flotation model is used to highlight the effect of turbulent dissipation energy on attachment and detachment rates. Preferential collection zones for ?fine? and ?coarse? particles are predicted for both forced air and naturally aspirated machines. Keywords: CFD-based model, attachment, detachment, energy dissipation, hybrid energy flotation?, forced air, naturally aspirated

Sep 1, 2012

By Peter Kondos

The need for a sustainable development of ore deposits makes it imperative to be innovative and mindful in creating an economically and environmentally viable operation, while maintaining a good working relationship with the various stakeholders involved in developing and operating a large and complex mining project. This is becoming immensely important as gold ore deposits are becoming more mineralogically complex along with lower grades presenting both metallurgical and environmental challenges that need to be addressed in mitigating risks and improving project economics. This paper presents Barrick?s approach to development of strategic technologies for our long-term sustainable growth through conversion of valuable resources into reserves for both our green-field development projects and the expansion of our existing mining operations. Some of the key strategic solutions, including mineral processing, metallurgical and energy technologies, developed by Barrick and their impact on some of our complex gold and copper-gold ores will also be discussed in this paper. Keywords: gold ores, copper-gold ores, processing, breakthrough technologies

Sep 1, 2012

By M. Prasad

Growing concern over increased levels of atmospheric carbon dioxide has prompted new interests in development of materials and techniques for its sequestration. Various research and developmental work on different aspects of carbon capture technology are being extensively carried out worldwide. The main objective of the present work is to synthesize a HAS material having high capacity and robust ability for recycling to capture greenhouse gases with special reference to carbon dioxide (CO2) from the sources from where it is released to the atmosphere. Existing CO2 capture techniques involves the use of solid materials that lack sufficient stability for repeated use or liquid adsorbents that are expensive and require significant amounts of energy. Keywords: greenhouse gases, carbon capture, solid adsorbent, HAS material

Sep 1, 2012

Vanadium-titanium magnetite from Panzhihua was crushed with open and closed circuit process by high pressure grinding roller (HPGR). The particle size characteristics of the crushed product were analyzed and the micro-cracks generated by HPGR during the crushing process were studied. The results showed that, in crushed products, the reduction ratio increases and the size distribution becomes more uniform with increasing of the pressure on roller?s surfaces. The fine fraction content of crushing products from -3.2 mm classification closed-circuit by HPGR increases obviously compared with that by Jaw Crusher and particle size distribution is more uniform. Large amount of intra-crystalline cracks and cleavage cracks are generated in vanadium-titanium magnetite crushed by HPGR, which makes the specific surface area larger and Bond grinding work index (objective particle size is 0.074 mm) decreased by 14.05% than that by Jaw Crusher. And the liberation degree of monomer of the product crushed by HPGR increased compared with that by Jaw Crusher with the similar fineness of grinding. Keywords: iron ore, high pressure grinding roller, micro-crack

Sep 1, 2012

By A. Sand

Within stamp-charged coke making a large volume of coal is compacted to one single coal cake before entering the coke oven chamber. This is done by means of several falling stampers in a stamping machine having a mold nearly of the oven?s dimensions. Producing a high quality coke also from inferior coals requires a cake density of approximately 80% of the coal density. Besides that the industrial stamp-charging process demands a minimum mechanical strength of the coal cake to move it from the stamping mold into the oven chamber without failure. Densification and the build-up of cake strength were investigated earlier in stamping tests using a micro-stamping device. The quantities derived from these tests (as e.g. cake density or porosity) represent average values for the entire cake. Statements describing the local compaction state at different heights are difficult to achieve without destructing the cake. In order to gain better insight into the densification process and the inner structure of the coal cake a computational model based on the discrete element method (DEM) has been set up using 2 and also 3-dimensional simulation software. The stamper?s position and velocity as well as the force acting on the stamper were monitored and the model?s response was compared against measurement data from laboratory stamping tests. It was possible to reproduce the force and displacement pattern of the stamper in response to the viscoelastic properties of the cake using standard DEM bonding and contact models. Furthermore, the rearrangement of particles in response to the compaction by the stamper was tracked by calculating their displacement at the point the stamper hit the coal surface. The latter can also be used as indicators of particle deformation or breakage. By defining control points at different heights the particle displacement, stress and strain rates, porosity could be studied at different heights. Keywords: coke making, coal stamping, compaction, agglomeration, DEM, simulation

Sep 1, 2012

By S. P. Das

Tumbling mill is an important unit operation in a mineral processing industry whose operation needs to be understood to make it an energy efficient unit. One of the important mill parameters is the impact spectra generated by collision of the moving charge mass on the mill shell. This process also generates mechanical vibration on the mill shell and propagates to the plumber block of the mill. In this work, we tried to understand the impact spectra by using different minerals such as Banded Hematite Quartzite (BHQ), Hematite and Quartz as mill feed of a semi-autogenous (SAG) mill. The said mill is of 1000 mm diameter and fitted with a force sensor on the mill shell and a vibration sensor on the plumber block. The analysis of the impact spectra was done by taking into consideration the peak impact force above a certain threshold value. It clearly shows that the impact force decreases as the particle size become finer irrespective of the mill feed material. This can be used as an effective tool by the mill operators to have an understanding of the mill product size reduction. The mechanical vibration tapped by a tri-axial accelerometer was analyzed by power spectral density analysis. The vibration signal analysis shows the variation in the power spectrum magnitude both at lower and higher frequency. It also shows inconsistency in case of BHQ where it shows a significant decrease in vibration at lower frequency and increase in vibration at higher frequency. Therefore, the impact spectra analysis is a better method compared to vibration analysis in understanding the mill product size reduction.

Sep 1, 2012

The flotation efficiency of magnetic concentrate of the Anhui hematite ore, which includes a great quantity of iron-bearing silicates, has been studied through reverse flotation test with a new type of collector Fly-102. The results indicate that collector Fly-102 has a strong adaptability to the variation of temperature, when the flotation temperature is in the range of 10? to 35?, using collector Fly-102 can obtain good flotation indexes. Collector Fly-102 has a strong adaptability to the variation of the slime contents and grades of the flotation samples. When the content of slime and the grade of the flotation feeds are 30% and 55.63% respectively, under the condition that the temperature is 15?, the open circuit flotation test was carried out with collector Fly-102. After one-stage roughing, one-stage cleaning and two-stage scavenging, a better result is got, the grade of iron concentrate reaches 67.12%, and the recovery of iron concentrate comes up to 84.15%.

Sep 1, 2012

By Shibayama A.

In this research, an investigation of a process to selectively remove arsenic (As) and antimony (Sb) contained in enargite (Cu3AsS4) and tennantite/tetrahedrite ((Cu1,Fe)12(As,Sb)4S13) copper resources by leaching and precipitation were performed. First in the leaching process, the target was to selectively leach As/Sb and reduce their contents in the ores to <0.5 wt% followed by a second process to remove As/Sb dissolved in solution for environmental control. Enargite ore contained 3.65 wt% As while tennantite/tetrahedrite ore contained 5.40 wt% As and 4.85 wt% Sb. Alkaline leaching using NaHS?NaOH media at varying experimental conditions (temperature, pulp density, time, reagent concentrations) were performed to investigate the process. As/Sb precipitation studies were also performed to control high As/Sb concentrations in leach solutions by using elemental sulphur (So). Results from leaching studies showed that over 99% of As/Sb in the impure copper ores can be removed and their contents in the final solids reduced to <0.5 wt%. It was also established that such very high leaching could be achieved at 80°C within 1?6 h and pulp densities as high as 1000 g/L. The study also revealed that leach solution containing very high As/Sb concentration ranging from 5 to 20 g/L can be used as fresh solution for leaching of fresh ores until concentrations exceeding 35 g/L when it was sent to precipitation circuit for As/Sb removal. Addition of elemental sulphur at 90°C and fast cooling to 30°C allowed over 60% As/Sb precipitation and removed as Na3AsS4 and solution with reduced As/Sb concentration to leaching circuit for continuous use. Keywords: Enargite; Tennantite/Tetrahedrite; Selective Leaching; Precipitation; Sodium hydrosulfide;

Sep 1, 2012

By B. S. Moroney

Elemental distribution varies widely in the ores, minerals and beneficiated products depending on the constituents. Accurate analysis of each element present in various beneficiated products is utmost required to assess the grade in view of zero waste technology. Hence, the suitable methods and instrumental technique is of prime importance as the distribution of various elements differs in the beneficiated products. Conventional classical technique of analysis is absolute and due to this, it has not become obsolete. Besides, it is much needed for making standards for various relative techniques. Instrumental techniques comprising of X-ray fluorescence, Induced Coupled Plasma Analyzer, Carbon-Sulphur Analyzer, Atomic Absorption Spectrometer etc. are important for quick and accurate analysis. However, the selection of these instruments depend on the nature of material to be analyzed. This paper highlights the importance and use of various methods/techniques and instruments involved in the analysis of various ores, minerals and beneficiated products. Keywords: wet classical, x-ray fluorescence, induced coupled plasma analyzer, atomic absorption spectrometer

Sep 1, 2012

By Z. S. Abisheva

Results of the study targeted to development of universal acidic-extraction-precipitation technology for gallium recovery from the sublimates are presented in the paper. This will let to utilize a new non-traditional source for gallium production. Phase composition of gallium containing dust was studied. Forms of gallium in the sublimates were determined. The main form is Ga2O3, however, GaP form is also present in the cottrel dust and Na5Ga3F14 form is present in the dust of aluminum electrolysis. The possibility of gallium concentration was established via secondary pyro-selection of the dust. Kinetics of interaction of dust components with sulfuric acid was studied. The products of the interaction subsequently were leached with water. Optimum conditions for direct leaching with HCl and H2SO4 were determined providing gallium recovery from the cottrel dust and the ash carry outs up to 95 %. Gallium recovery from the primary dust and the secondary dust of aluminum electrolysis was at 52; 64 % and 63; 83 % respectively. Effect of Fe, P, K, Na and Al admixtures for gallium extraction from hydrochloric acid solutions was studied. It was shown that gallium chloride complex (GaCl4-) is extracted into the organic phase from the following acid mixtures: HCl + H2SO4, HCl + H3PO4, HCl + H2SO4 + H3PO4, HCl + HF. Kinetic regularities of gallium extraction in the system (tri butyl phosphate) TBP ? HCl - Ga were studied using diffusion cell method with agitation. Optimum conditions for gallium extraction from complex hydrochloric acid solutions with TBP were found providing 99.9 % recovery and separation coefficient for gallium and iron (III) of more than 25 in one stage. Sodium hydroxide and water were selected as reagents for re-extraction of gallium from the organic phase. Different options for disposal of by-products that are formed in the processing of cottrel dust, ash sublimates and dust of aluminum electrolysis were proposed and tested. Keywords: gallium, kinetic, sulfatization, leaching, extraction, technology

Sep 1, 2012

By M. Alvarez-Silva

The control of the amount of chromite reporting to the concentrate during the flotation of UG2 ore is of critical importance since its presence affects the downstream smelting process. It is generally reported that the main mechanism responsible for chromite recovery is through entrainment. This is reflected in analyzing the solids and water recoveries. These in turn are strongly dependent on the froth phase. In the present investigation a laboratory scale column flotation cell was used to investigate the role of the froth phase in the flotation of UG2 ore. Such a device is superior to a standard batch cell since it operates at steady state in open circuit and also allows for a greater degree of flexibility in terms of froth heights. The mass of solids and water recovered in the concentrate as well as chromite (Cr2O3) recovery by size class was determined as a function of froth height, superficial gas velocity and depressant dosage. The results showed that depressants had little effect on chromite recovery but increased the grade due to the depression of gangue minerals. A 60cm froth height always resulted in slightly lower solids, water and chromite recovery than for 30cm. Typically only 20-25 % of solids reaching the pulp-froth interface reached the launder. The relationship between solids and water recovery for a wide range of conditions indicated that chromite is mostly recovered by entrainment. Keywords: UG2 ore, column flotation cell

Sep 1, 2012

By Nikkam Suresh

Dense medium cyclones have been in use for washing coarse and small coals for more than 50 years. There have been modifications in its design and today these units have become indispensable for washing of Indian coals possessing difficult washing characteristics. About 53 percent of the Indian coals (coking and non-coking) are being washed in jigs, about 38 per cent are washed in dense medium cyclones while the remaining 9 per cent is treated in other units like Barrel Washers, Heavy Media Baths and Drum Separators etc. The present paper deals with the attempts made for design of industrial Dense Medium Cyclones for enhanced coal recovery. Two industrial units of 500 mm diameter and 650 mm diameter were designed with their washing capacities being 200 m3/hr and 350 m3/hr, respectively. The results of the pilot tests conducted on 500 mm cyclone treating very high Near Gravity Material coals crushed to -3.0+0.5 mm gave an ash reduction of up to 19.5 percent with the new design i.e., from a feed ash of 34.5 percent to 15.06 percent in clean coal with an appreciable yield of 45 percent in one stage.

Sep 1, 2012

By Kwang Soon Moon

Liquid ? liquid reactions such as solvent extraction in hydrometallurgy and BTX extraction in petrochemical industry has long suffered from the long retention time mainly due to the limited interfacial area caused by the immiscibility between water and oil phase, requiring typically very large perfect mixer type reactors and tall adsorption towers. A novel spray reactor for immiscible liquids; that is the KISEI Nozzle Reactor (KNR) was introduced, enabling the drastic increase in the interfacial area between the reacting immiscible liquids. Various spray mechanisms were applied in materials processing, e.g. spray drying, powder metallurgy, and aerosol industry, but not in hydrometallurgy. The KISEI Nozzle Reactor(KNR) was fully developed and used in production of biodiesel from the immiscible triglycerides and methanol. An experience with a full production plant facility is briefly discussed in the current paper. With the fog-like methanol spray in oil medium, the trans esterification reaction was almost instantaneous, and transformed the traditional batch trans esterification process into a continuous production process. And above all, with no moving parts in the KISEI Nozzle Reactor (KNR), the process requires minimal operation and maintenance costs. Keywords: immiscible liquids reaction, nozzle spray reactor, continuous biodiesel reactor, hydrometallurgy, organic extraction, micro emulsion

Sep 1, 2012

By C. V. G. K. Murty

Sillimanite, chemically named Aluminum silicate, 3Al2O3SiO2 is one of the three forms of alumino silicate polymorphs and commonly encountered in aluminous metamorphic, plutonic, and volcanic rocks and their weathering products. Most of the sillimanite deposits are granular and are of high grade available in coastal areas as associated mineral along with Titanium bearing minerals namely ilmenite, rutile etc. Sillimanite is one of the widely accepted raw materials for the manufacture of high alumina refractories (55-60 % alumina) or bricks. Sillimanite based refractory bricks are used for the lining of Blast furnaces, Arc furnaces, Soaking pits, Reheating furnaces of iron and steel, rotary kilns for cement manufacturing and general kilns for lime production. Considering the vast potential of unexploited sillimanite reserves in India, M/s Trimex Sands Pvt. Ltd., (TSPL)has set up a Mineral Sand Processing plant in 2010 at Andhra Pradesh with a capacity to produce about 50,000 tons of sillimanite per annum besides the production of various heavy minerals such as ilmenite, rutile, zircon and garnet. Traditionally in India, sillimanite is upgraded by froth flotation technique using Oleic acid as a collector cum frother, sodium silicate as depressant and soda ash as pH regulator. At TSPL, Conventional mechanical float cells are installed to float sillimanite. In addition to the usual problems associated with conventional cells, poor flow ability of the sillimanite concentrate is experienced in dry circuit due to the presence of sodium oleate. Fine garnet in the sillimanite concentrate contributes to high iron content in the final product, making sillimanite separation a nightmare for operators (lower recoveries coupled with inferior grades). Various efforts were made to improve the performance of the circuit such as introduction of additional frother like MIBC, optimizing the operating parameters such as pulp density, collector dosage, depressant dosage, air flow rate, pH etc., use of collector aids, stage wise addition of reagents etc. The challenges faced to produce a sillimanite product with stringent quality norms and the efforts made to improve the grade and recovery are described in this paper. Keywords: sillimanite, froth flotation, conventional mechanical cell

Sep 1, 2012

By R. C. Dunne

As ore grades of existing and new ore deposits continue to decrease there is ever increasing pressure to decrease operating costs to maintain profitabitabitiy at existing mine sites and for new projects. The accepted solution to this dilemma in most cases is to increase treatment rate, leading to a coarser grind, at the expense of marginal decreases in recovery. The recovery loss is usually associated with losses of liberated and composite coarse material. This paper will review the practice of coarse particle flotation, including the reagent chemistry, cell hydrodynamics, froth stability, entrainment and flotation cell design, all parameters important to the recovery of coarse liberated and composite particles. This will provide a better understanding of opportunities to improve the recovery of coarse particles. Some examples will be provided.

Sep 1, 2012

By M. R. Garmsiri

With the environmental issues and water recycling becoming more significant, the development of deep cone thickeners has improved the efficiency of thickening. While deep cones performance is dependent on many factors, the sensitivity of an industrial thickener to each variable factor has not been determined. In this work, four industrial deep cone thickeners, which are used on tailings stream in Shahrebabak Copper Complex, were monitored for a year to analyze the effectiveness of different factors affecting the performance. Feed flow rate, fine fraction of the feed, solids concentration, flocculant dosage and concentration, solids density, pH, temperature and bed height were the factors investigated on the basis of partial R2 and partial correlation. Results indicated that, with positive effect, feed slurry dilution affected the dewatering efficiency most sensitively. With a negative effect, the sensitivity of dewatering efficiency of deep cone thickeners to flocculant dosage was negligible. While, decreasing flocculant solution concentration had a considerable positive effect.

Sep 1, 2012

By Arkady Senchenko

The application of centrifugal separation methods with the use of gravity concentrators has been assigned high priority while gold-containing minerals processing. The separation proceeds under centrifugal force resulted from the rotor spinning and wash water flow in the concentrators. The high specific gravity particles are retained at the trapping surface of the cone, and the low specific gravity particles are brought in the tailings. The centrifugal field in such concentrators (Knelson, Falcon) is generated by the rotating cone provoking the swirling of the free fed slurry flow. The author investigated the regularities of the separation process in the centrifugal gravity concentrator where a two-phase flow of the separated mineral media is under the pulsed pressure of the fluidization water and air. As a result of the study the possibility of the deeper penetration of the fine heavy fraction into the cone rings, providing the fluctuation of the fluidization water or air flow, was theoretically argued and experimentally proved. This allows the increase of the separation performance at low pulsation costs. The developed mathematical models are in close conformity with the actual process of interest and they enable the prediction of the heavy phase behavior at the isolated process stages in the concentrator. Keywords: gold, centrifugal gravity concentrator, containing, specific gravity, cone ring, pulsation, cost, fluidization water, Knelson centrifugal separator

Sep 1, 2012

By Tomasz Niedoba

Coals occurring in nature are characterized by various properties. According to Polish norms, the classification of coals taking into consideration their calorific value contains coals from type 31 (flaming coal) until type 43 (meta-anthracite). The samples of coal of type 31 were taken for investigation. To this purpose, the approximations of ash contents and density distribution functions were done for this coal type (determination of marginal distribution functions). They were the basis for application of so-called Morgenstern distribution functions to approximate the function Z=L (?), where Z is ash contents and ? - coal density. Then, the comparison between obtained results was performed and the results were statistically evaluated. They are the basis for the further research of other types of coals.

Sep 1, 2012

By V. Dementiev

Pyrite cinders is a complex raw material, in which the valuable metals are: Au(2.04 g/t), Ag(35.0 g/t), Cu(0.38%), Zn(1.1%) and Fe(56.0%). In this case high costs for mining and ore processing are not required. The hydrometallurgical treatment of pyrite cinders using thiourea, sulfite and cyanide solutions are examined in this paper. It was found that thiourea leaching is ineffective due to high consumption of thiourea and sulfuric acid. The cyanidation on pyrite cinders was conducted. Various options of the preparation of the products for the subsequent cyanidation have been examined. The tests on cyanidation process optimization were conducted. The effectiveness of these cementation methods by metallic iron or extraction for copper recovery from water phase has been shown. Zinc precipitation can be found in the form of carbonate. In order to recover noble metals from cyanide solutions, the cementation onto zinc dust was tested. The developed technology provides for recovery at 49-56%Au, 20-25%Ag, 22.5%Cu and 50%Zn during NaCN (1.4 kg/t) and CaO (6 kg/t) consumption. The results of pilot plant testing are the basis for technical regulations in order to design a pyrite cinders treatment plant. The technology has been examined in pilot-plant conditions. In this case the recovery of 54.5%Au, 45.3%Ag, 30%Cu and 49.9%Zn was achieved to provide saleable products. Keywords: pyrite cinders, thiourea leaching

Sep 1, 2012

By T. Bhambhani

Research at Cytec over the past two decades has shown that the traditional approach for ore metallurgical characterization (typically conducted via laboratory-scale batch flotation tests), which involves changing reagents and conditions one-factor-at-a-time, leads to several pitfalls. The chemical solution thus selected has a narrow un-optimized window of performance and will likely fail in the plant. A holistic approach, called the Flotation Matrix 100? process for ore metallurgical characterization, was developed at Cytec about a decade ago and has been successfully used to develop robust reagent solutions for several operations around the world. The premise for the approach is that flotation outcome from ores is variable and is determined by complex interactions between various physical, chemical and operational factors. A key component of the process is the use of efficient multivariate designs focused on the chemistry aspects (reagents and pulp chemistry), which helps identify the best processing conditions for each ore type, as well as the conditions resulting in poor performance. It also includes advanced statistical methods for dealing with the complexity and variability of experimental data. The holistic approach is illustrated in this paper with a case study on Pb/Zn ores. Using just 18 carefully designed batch tests, it is possible to partially simulate the behavior of each ore type in the plant. The best conditions for each ore type, along with the conditions to avoid, are identified. Along with this, insights are obtained into the reasons for high reagent dosages for certain ore types, and interactions between variables. Keywords: flotation, holistic approach, metallurgical characterization, multivariate experimental designs, base and precious metals recovery, sulfide collectors and modifiers, Pb/Zn sequential flotation

Sep 1, 2012