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By Vladimir Vigdergauz, Elena Belogub, Dmitriy Makarov

The influence of supergene oxidation on physicochemical and technological properties of polysulfide ores was studied. Modeling and analysis of oxidation pyrite copper-zinc ore samples from the Valentorskoye deposit show that sulfide floatability is decreased by the longer-term oxidation. The treatment of oxidized samples by sulfuric acid in oxidative conditions and its impact on the elemental sulfur composition on the surface of sulfides was discussed. It is shown that an enhancement of the floatability of sulfides of oxidized polysulfide ores after leaching by sulfuric acid could be perspective for the developing of combining floatation-hydrometallurgical technology of the nonferrous metals recovery.

Jan 1, 2014

By J. Kwon, D. Lee, H. Cho

"The use of the combined grinding and liberation model to predict liberation characteristics of iron ore comminuted by a ball mill was studied. Comminution characteristics were obtained using the one-size fraction method. The iron ore samples were crushed and separated into a number of narrow size fractions by screening. The size fractions were further divided by magnetic separation into three classes: concentrate, middling, and tailings. Subsequently, various size-grade classes were subjected to ball milling, and the results were analyzed in terms of the kinetic grinding model. The mineralogical textures of the grinding products were analyzed using mineral liberation analysis. The distribution of iron content within the size fractions was characterized by the beta distribution combined with the Andrew–Mica diagram. It was found that the grinding characteristics of the iron ore samples varied slightly with the iron content. However, the liberation characteristics were well described by the same set of liberation model parameters, regardless of composition. The variation in grinding kinetics with composition and the liberation model parameters was used in the combined comminution–liberation model to predict the evolution of the size-composition matrix as grinding proceeded. The predicted results agreed well with the experimental results. The developed model can be used to construct the yield–recovery graph and to calculate the liberation efficiency to determine the size reduction threshold for efficient separation. INTRODUCTION In mineral processing, comminution is usually the first step that ores undergo to liberate valuable minerals from gangue minerals. Generally, as the particle size decreases, higher liberation can be achieved. However, excessively small particles are unfavorable to subsequent processes, such as separation. Moreover, comminution is a highly energy-consuming process itself that accounts for approximately 60% of all energy used for processing. Therefore, there is a definite need to increase energy efficiency by applying adequate stress so that a high degree of liberation can be acquired at the coarsest size without overgrinding. To this end, it is essential to develop a model to predict the liberation of minerals as a function of size reduction."

Jan 1, 2018

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 Arkady Senchenko

The paper deals with the problem of refractory gold-containing material processing. It is observed that all traditional methods for liberation of fine gold from this type of products are characterized by a number of essential disadvantages, where the main ones are ? considerable expenses for ore processing and big environmental impact. As an alternative to the existing methods there is considered a gold liberation method, which is based on the combination of ultra fine grinding process with the consequent atmospheric oxidation. The theoretical justification of atmospheric oxidation was carried out, in the result of this the mechanism and the degree of sulphide minerals? oxidation was found out, the dependence of gold dissolution speed on the slurry content in liquid phase produced by grinding and oxidation was identified. The experimental data and results of pilot-plant testing are given and the most effective grinding and atmospheric oxidation mode is selected on this basis. The performed complex of research works allowed us to use the provided technology at the gold processing plant having capacity of 8 mln. tons of ore per year. The questions, problems, advantages and disadvantages of atmospheric oxidation technology for refractory gold-containing concentrates are considered in this paper. Keywords: refractory gold-containing material processing, gold liberation method, cyanidation

Sep 1, 2012

By N. Ahmed

This paper is concerned with the drainage behaviour of gangue mineral in the froth phase. Experiments were carried out in a continuous laboratory flotation cell in which froth depth and bubble size could be changed independently. The fraction of solids returning from the froth to the pulp zone was expressed using a rate constant. A mixture of hydrophilic solids (silica) and floatable particles (glass ballotini) was used as a flotation feed. Samples of glass ballotini of different hydrophobicities were obtained, using controlled silanation. Three samples, with contact angles of 50, 66, 82 degrees, were used. The effect of the initial bubble size (pulp bubble size), concentration of gangue mineral in the froth zone, and froth depth on the drainage of silica, were investigated. The drainage rate of the entrained solids increases with an increase in the degree of hydrophobicity of the floatable particles. Concerning the effect of pulp bubble size on the drainage rate of entrained solids, larger bubbles always give higher drainage rates due to formation of relatively loose froth structures which allow gangue particles to easily move down to the pulp zone. Conversely, smaller bubbles exhibit lower drainage rate constants, in particular at shallow froth depths.

Jan 1, 2003

By A. Oberrauner

Electrostatic separation is a dry separation technique usable for many applications in the mining- and recycling industries. At the Chair of Mineral Processing intensified research has been done on this topic during the last years. One challenge was to measure the triboelectric charging of fine mineral particles in a triboelectric charging device consisting of an electrically insulated polyethylene rotor/stator assembly. These tests, performed on monomineralic samples, were accomplished in a climate chamber. It was shown that charging of minerals not only depends on rotor speed, feed rate and atmospheric circumstances but also on the properties of the applied electrostatic field. Tests on pure calcite in contact with the polyethylene rotor/stator system resulted in specific triboelectric charges up to +10 nC/g at low relative humidity. With more water present in the surrounding atmosphere, these charging values decreased significantly. However, at higher relative humidity, triboelectric charge values could be maintained after an electrostatic field of positive polarity was applied. Similarly, charging behavior was found with other hydrophilic minerals. The idea behind all these tests was to find the largest charging difference between minerals occurring together in a deposit and to be able to charge them oppositely, assuming that this means good sort ability in an electrostatic separator. The results gained from these investigations are shown. After having obtained many results on charging pure minerals, it became interesting to test the applicability of the charging tendencies on electrostatic separation of fines <100 µm. In order to do so, a separator for fine polymineralic powders was developed, constructed and combined with the triboelectric charging device, all being set up in a climate chamber. This new so-called coax-separator is presented along with first test-results.

Sep 1, 2012

By Gus Van Weert, Samuel A. Bolorunduro, David B. Dreisinger

"INTRODUCTIONAcid pressure oxidation of high-grade natural acanthite was investigated in the range of 110-150°C and in the sulphate media. High acidity and low pulp density were used to prevent the precipitation of silver.RESULTS AND DISCUSSIONTwo sets of acanthite specimens were obtained from La Valenciana and Ingleterra mines, Mexico. Pressure oxidation tests were conducted on 1 litre scale in a standard 2-litre Parr titanium autoclave.EFFECT OF TEMPERATURE ON THE REACTION OF ACANTHITEThe effect of temperature on the rate of oxidation is presented in Figure 1. The rate of reaction increased with increasing temperature."

Jan 1, 2003

By Sung. Hyejin, Kyoungkeun Yoo, Oh-hyeok Kown

The sediments near coasts and ports in Korea have been found to be contaminated with heavy metals and organic matters. So far the sediments have been dumped to landfill sites or ocean. However, the number of available landfill sites is decreasing and ocean disposal of wastes was strictly prohibited. Although physical separation processes have been found to be useful for the remediation of contaminated soil with heavy metals, because the sediments consist of fine particles, it is difficult to remove heavy metal component by physical separation processes. Furthermore, the sediments contain organic matter, so there is a concern about strong stink during the sediment treatment. The present study is aimed to develop the treatment process for removing heavy metals and organic matter from the contaminated sediments. The heavy metals and organic matter were oxidized and dissolved by electro-generated chlorine, and the chlorine used is regenerated and circulated in the leaching process. This system has economic and environmental advantages to reduce the wastewater and the oxidant consumption. The leaching results show that the metal removal efficiency increased to more than 99%, and more than 50% of organic matter was decomposed.

Jan 1, 2014

By Leon Lorenzen, Trevor J. Britz, Pierre J. Van Zyl, Ellis R. Els

Enhanced granulation of UASB granules was tested on pilot scale with two different test reactors (about 5 litres capacity each). Sludge from a local sewage works was used, with peach cannery effluent as carbon source. Cyclic motion of the reactor contents, and a daily replenishment of feed material create the necessary stress conditions for enhanced growth. Sizable granules, bigger than 0.5 mm, were produced within 20 days. Of the two reactors tested, the reactor equipped with a horizontal agitation shaft proved more effective.

Jan 1, 2003

By S. K. Pan, M. P. Srivastava, N. Prasad

"Dalli mines of Bhilai Steel Plant, India is fully mechanized iron ore mine having wet processing system. It has a capacity to treat 5 Mt of ROM. In processing circuit of Dalli mines, scrubbing, wet screening and classification operation is being carried out. Average slime generation for the last five years is about 14% of ROM. As the mining has reached to the lower benches, fines generation is more. As a result, very fine and heavy particles, which settle fast, are being discarded with the slime to tailing pond. These heavy and faster settling particles were causing jamming in the thickeners.Laboratory investigations were carried out at Research and Development Centre for Iron and Steel (RDCIS) to suggest a suitable scheme to recover high quality fines so that the availability of thickener can improve. The slime samples were first treated in a floatex density separator. The concentrate obtained from the floatex density separator was treated in hydrocyclone. Laboratory investigations indicated that the slime with 49% Fe, 12.7% silica and 10.7% alumina can be upgraded to 62.1% Fe, 3.3% silica and 2% alumina with 36% material recovery. Based on the laboratory studies ,a system was installed at Dalli minesThe general arrangement of the system is shown in Fig. below."

Jan 1, 2003

By Sebastian Fredes, Williams Calderon, Mauricio Toledo, Gonzalo Montes-Atenas

The influence of the temperature on leaching kinetics of copper-bearing minerals has been widely acknowledged: the leaching of copper oxide ores is generally described as exothermic reactions while copper sulfide ores are associated with endothermic reactions. Reports studying the influence of temperature on leaching kinetics at laboratory scale frequently involve the implementation of either fully flooded isothermal systems or jacketed column setups. Nevertheless, at industrial scale controlling or monitoring the temperature or temperature changes is almost impractical. In fact, leaching process is usually a large tonnage operation and changing the temperature of vast amounts of material would require an enormous amount of energy and highly specific heat transfer equipment. Preliminary computations on the amount of energy required to increase the temperature of a heap or dump in 1°C indicates that it would be impossible to find an energy source able to accomplish the task. In order to provide a solution to this matter it is suggested to create an energy managing protocol (EMP) that permits heat up or down the porous body locally taking advantage from the temperature gradients and from the reactivity of different regions within the material as a function of the leaching cycles. The aim of this study is to evaluate different heat transfer regimes in a 1 ton pilot column leach operation. It was found that best results of copper recovery are obtained when heating up the column in horizontal bands starting from the top of the column moving downwards as the leach cycle evolves. The system is expected to be suitable for industrial applications, but further development of the technique is required, particularly in the design of the heat transfer dispositive.

Jan 1, 2014

By Douglas Fuerstenau

"Comminution not only is the major energy cost in mineral processing but it also can limit the grade of ores that can economically be processed. Rittinger first postulated that the energy for comminution is proportional to the new surface produced. Because most of the strain energy needed to initiate and propagate cracks in particles cannot be recovered, researchers reported woefully low comminution efficiencies. Recognizing this, Schoenert proposed that the baseline for assessing comminution efficiency should be the mechanical energy needed to break single particles. After extensive single-particle studies, Schoenert turned to comminuting beds of particle in piston dies. Finding particle-bed comminution to be energy efficient, he had the brilliant conception of making the process continuous, namely his invention of the choke-fed high-pressure roll mill (HPGR). Practical comminution involves masses of particles, which can lead to energy efficiencies far less than that of single-particle breakage. A three-way classification of grinding modes in terms of the mobility of the particle mass provides the necessary insight into the low efficiency of different comminution machines: namely, single-particle breakage, confined particle-bed grinding (HPGR), and loose-bed grinding (ball mill). Examples are given for determining and comparing comminution efficiencies. The size distribution of comminuted products become self-similar, and a single parameter, the median size, can be used to quantify the extent of comminution. The reduction ratio, expressed in terms of the mean size of the feed and product, varies linearly with expended energy and the slope of such plots is a measure of the grindability of the mineral. This approach clearly gives the order of energy efficiency as single-particle > particle-bed > loose-bed comminution. HPGRs are more efficient at low reduction ratios but lose that advantage at higher reduction ratios. Extensive hybrid grinding experiments carried out with our instrumented ball mill and HPGR showed significant energy savings by first comminuting the material in the HPGR and followed by the ball mill. At Cerro Verde an industrial-scale hybrid HPGR/ball mill system is reported to have a 13 percent energy savings over a SAG mill/ball mill system."

Jan 1, 2014

By V. Avzian Belozersky reg 453524, Vasily V. Lodeischikov, Adolf F. Panchenko, Til E. Vidusov, Olga D. Khmelnitskaya, Vladimir E. Dementyev

"Presently, there is a number of gold deposits which cannot be developed using the conventional technologies with acceptable economic indices due to low gold content, high depth of ore occurence and other conditions. For such ores, an innovation technology of underground gold leaching in the place of their occurrence is of special interest. The technology excludes ore mining and hoisting to the surface. This enables the production cost of 1 g of gold to be considerably reduced in comparison with conventional methods of gold recovery.The Maminskoye deposit oxidized ores were chosen as the subject of underground leaching because they are ideally suited for this purpose due to their composition and hydrological parameters. The ore reserves within the underground leaching block are 90, 000 t with 0.7 g/t average gold grade.An experimental system for underground leaching with a throughput of 15 cubic m solutions per hour was developed. A combined filtration-and-infiltration system of the ore massif development by holedrillingwhere pregnant solutions are air-lifted was worked out.The underground leaching flowsheet includes Au dissolution by chlorine-containing solutions, Au adsorption from solution onto active carbon, carbon concentrate ashing and calcine melting to produce Dore metal."

Jan 1, 2003

By P. M. Solozhenkin, V. P. Nebera, V. D. Skorohodov

"Aqueous dispersions of air specifically prepared on the basis of flotation reagent solution acquire active properties in relation to the solid surface and may be imply as a medium for flotation ores. Such aerated solutions were defined as Activated Aqueous Dispersions of Air (AADA) with 5-6:1 ratio and the procedure of mineral separation was defined as a flotation process under non-equilibrium conditions. These procedures differ from conventional flotation mainly in reagent interaction with minerals through their adsorption films on gas bubbles simultaneously forming flotation complexes. Gas-liquid mixture is kept till an adsorption layer of reagents close to the limit value is formed on the surface of bubbles. The theoretical basis of AADA is considered.The results of two-phase gas- liquid mixture (AADA) were studied. Two versions of AADA were considered. Electrical surface potential of the air bubbles with the surfactant film, untreated minerals particles in Coulomb attraction and flotation complex formation were analyzed. Special flotation machines were constructed for separation of mineral suspension in air dispersion, whose effectiveness was confirmed in flotation of apatite waste of Kovdor ore. FK-9 machine introduced on Kovdor iron ore combine for the recovery of apatite from current departures of factory. The froth product contained 7.2 % P2O5, with recovery of 44 % apatite, which was processed for getting melted phosphoric-magnesium fertilizers."

Jan 1, 2003

By M. H. Moys, M. M. Bwalya

"INTRODUCTIONThe grinding rate prediction scheme makes use of the energy spectra output from the DEM simulations and the statistical quantification of material strength, which can be done using the drop-weight tester or some other similar equipment. The prediction scheme is evaluated using milling experiments performed under well-defined conditions.MATERIAL STRENGTH QUANTIFICATIONUsing the drop weight test machine, particles of a wide size range were broken singly using different energy inputs. A characteristic equation key to milling rate prediction that relates the probability of fracture with energy input and number of impact attempts was obtained and is stated as follows:"

Jan 1, 2003

By Nóra Schreithofer, Kari Heiskanen

"INTRODUCTIONThe knowledge of the adhesion forces between particles and bubbles is of key importance in the improvement of flotation models. The development of the Colloidal Interaction Force Measurement Apparatus (CIFMA) opened the possibility to quantify the adhesion forces between particles and bubbles. The aim of this study was to examine the effect of three main variables: the approach velocity, the loading force and the loading time on the adhesion force between an air bubble and a hydrophobized silica particle."

Jan 1, 2003

"The effect of operational conditions, such as air flow rate, impeller speed and solid concentration, as well as the effect of solids concentration and frother dosage, on the bubble size distribution produced in a lab scale flotation cell, were investigated. The cell was operated under batch conditions. The measurement of bubble size was accomplished using an automated photographic technique. The technique enabled fine and coarse bubble distributions to be measured in two-phase (liquid-gas) and three-phase systems (solid-liquid-gas). In each experiment, around ten thousand bubbles were characterized.This paper discusses the main results obtained using the new photographic technique and compares these with previous findings available in the literature. The results indicate that photographic techniques combined with digital imaging processing might become a standard technique for measuring bubble size distribution in flotation machines.HUT BUBBLE SIZE ANALYSERThe importance of having precise and reliable equipment for measuring bubble size distribution in industrial flotation machines has been widely recognized. The measurement of bubble size, particularly in three-phase systems, is rather complex due to the opaque nature of the pulp. However photographic techniques combined with ingenious sampling techniques are utilized for overcoming this difficulty. The technique named HUT, combines previously developed visualization methods with digital image processing procedures. In this technique bubbles and aggregates are exposed to a monochrome progressive scan camera. The acquired images are directly stored in a computer connected to the camera for post-processing. The sampling apparatus consists essentially of a vertical tube for collecting bubbles, a viewing chamber and a collection chamber, where particles carried by the bubbles are released. The function of the collection chamber is to maintain the viewing chamber clear for imaging purposes. Each image is automatically processed off-line, using digital image tools. In this paper the advantages and limitations of this new technique are described."

Jan 1, 2003

By Arkady Senchenko, Yuri G. Seredkin, Alexander Aksenov

"This paper describes the development of efficient technology for the treatment of complex ores containing gold and copper as major valuable components, where silver is present as well. Copper is mostly represented by oxidized minerals in these ores; however, copper sulfides are also present. Gold is present in its free form and in associations with oxidized and sulfide minerals; silver usually accompanies gold. Complex composition of the ore requires complex solutions for their treatment. The results of searching for the techniques to recover valuable components are described in this paper. Gravity methods allow for free gold recovery, flotation methods allow one to recover major part of copper and precious metals in associations; and in the result of leaching process additional amount of copper, gold and silver is reported to solution. Combining all these methods help achieving high levels of valuable components recovery. When implementing a combined technological flowsheet about 80 % of copper goes to concentrates from gravity and flotation of sulfide and oxidized copper minerals; and sulfuric acid leaching allows increasing total copper recovery up to 90 % and higher. Major part of precious metals (up to 90 % of gold and 80 % of silver) is recovered to these concentrates, and after hydrometallurgical treatment it is possible to increase gold recovery up to 96 %, silver recovery - up to 90 %. The suggested technology helps solving the problem of precious metals recovery from complex gold-copper ores, and allows treatment of the ore with different proportion of sulfide and oxidized minerals, and at different valuable components grade."

Jan 1, 2014

By R. Peter King, Claudio L. Schneider, Reiner Neumann

Predicting the liberation spectra that is produced from breakage of two-phase ores under the random fracture assumption can be accomplished by measuring the conditional, on length, linear grade distribution directly from images obtained from a representative sample of the unbroken texture. The technique tremendously simplifies the prediction problem by avoiding the multiple convolutions that arise from the traditional method based on a description of texture from a measurement of the chord length distributions associated with each phase in the unbroken texture. For a 3-phase system, the phase transition probabilities associated with the textural information make the traditional calculation an almost insurmountable mathematical problem. The direct measurement procedure on the other hand can be expanded to three phases comparatively easily.

Jan 1, 2003

By J. D. Miller, C. L. Lin

In general, x-ray computed tomographic (CT) techniques are able to provide 3D images of the internal structure of opaque materials in a nondestructive manner. The unique cone beam geometry allows acquisition of all 2D projections with only one rotation of the sample thus providing for fast data acquisition and better x-ray utilization, as a complete 2-D detector array receives the cone-shaped flux of rays. Thus, an isotropic 3D volume can be reconstructed without the mechanical translation and the stacking of sequential slices as is the case for more conventional CT scanners. In this regard, a state-of-theart, custom designed x-ray microtomography facility to provide very detailed 3D spatial analysis of multiphase particles has been installed and is in operation at the University of Utah. The reconstructed 3D tomographic volume allows for an adjustable spatial resolution from 5 to 20 microns for sample dimensions from 10 to 40 mm in diameter, respectively. For example, a packed bed of coal particles is shown below in which different crystalline froms of pyrite are distinguished in 3D.

Jan 1, 2003