Search Documents

By E. Barsky

Physical principles of two-phase flows with a polyfractional solid phase have not received a sufficient theoretical interpretation as yet. Two-phase flows in the separation mode with a counter-flow of particles are even more complicated. Only statistical methods give an insight into general regularities of such processes. These processes can be interpreted best by analogy with the statistical model of an ideal gas developed by L. Boltzmann, although here a number of difficulties arise. The notion of a statistical system for such flows is substantiated. A mathematical estimation of a statistical system is presented. New notions are introduced, namely, potential extraction of a system and lifting factor. A relationship having the physical meaning of entropy is derived for a two-phase flow in the separation modes. The connection of this new entropy with flow parameters, such as the number of particles, separation factor and chaotizing factor, is established. Properties of this entropy are analyzed, as well as the analogy and difference between this entropy and Boltzmann?s entropy. The notion is formulated and the definition of the chaotizing factor of a process is suggested. In the framework of a statistical approach to two-phase flows in the separation mode, the notion of flow mobility has been formulated. Principal regularities of mass transfer in zone/apparatus sys-tem are analyzed. Principal ideas of a cellular model of the process are formulated, and main relationships for its description are derived. Proceeding from the cellular model, a dependence describing the degree of fractional separation of a narrow size grade is found. The analysis of this dependence makes it possible to reveal the crucial role of the Froude criterion for gravitational separation processes. It is found empirically that this parameter is a basis for the affinization of separation curves (Barsky E, Barsky M, 2006; Barsky, 1980).

Jan 1, 2014

By T. Damyanov

Spherical grinding media (balls) are the most widely used media for comminution of ores by grinding. A modelling simulation study of the behavior of two grinding media in the grinding process was conducted to determine the possible advantages of the new shape milling bodies called tetraballpebs. Tetraballpebs are in the shape of tetrahedrons with spherical convex walls. A three dimensional CAD model of the mill drum with a diameter of 1200 mm was used. A continuous operating mode was simulated in terms of the 3D contact elements of the model (milling bodies and mill drum). Simulation tests were carried out in a typical grinding mode and at a typical rotational speed of the drum mill (75 per cent of the critical speed in cataracting mode). Studies carried out with both grinding media include equal number of milling bodies with the same weight and volume. Having thus ensured a uniform mass of the grinding media and same number of milling bodies, and constant other conditions and process parameters, conclusions can be drawn about the influence of the shape of the milling bodies on the grinding process. A kinematic analysis of the system using CAE (computer-aided engineering) model parameterization was conducted. The controlled parameters are: ? Power draw; ? Kinetic energy of each milling body; ? Motion of milling bodies inside the drum Keywords: grinding, grinding simulation, balls, tetraballpebs, DEM, CAD-CAE

Sep 1, 2012

By Ari Kokko

Metso has a long history supplying boilers for high ash coal firing. These boilers are based on circulating fluidized bed (CFB) technology. CFB?s biggest benefit is fuel flexibility ? it can burn fuels from high moisture content to high ash content. Metso has delivered tens of CFB boilers burning waste or high ash coal starting on 80?s. Some of the boilers have been in operation twenty years meaning that there is a long term experience from these plants available. This feedback includes boiler performance and maintenance issues of the boiler. Metso is also delivering coal washing plants to improve coal quality, i.e. reducing ash content of the coal. The idea to combine coal washing plant and CFB boiler was made up two years ago in Metso. Up-coming legislation of coal washing and restrictions for washery reject land-filling in India are good drivers for this kind of concept. Pre-study of this kind of concept led to the conclusion that coal washing process can be fine-tuned so that reject?s calorific value is only 1100 kcal/kg and that was set as a target for boiler design. Metso shipped 200 tons of washery reject to its own research center located in Tampere Finland. First a wide range of fuel characterization tests were done in lab-scale and after that one week test run in 4 MW CFB pilot boiler was done. Test run proved that 1100 kcal/kg can be fired without any support fuel with special boiler design. Test run results gave a good set of data regarding combustion efficiency, emission performance and boiler dynamic behaviour when burning this kind of fuel. These results are introduced in this paper. This paper introduces also the CFB boiler concept for washery reject firing including boiler plant, fuel and ash handling systems and flue gas cleaning system. Power plant can be integrated with coal washing plant so that boiler size matches with washing plants c

Sep 1, 2012

By E. V. Koporulina, E. L. Chanturiya, M. V. Ryazantseva, E. S. Zhuravleva

"The morphology of the surface of sphalerite, galena and chalcopyrite and the adsorption of butyl xanthate under conditions of preliminary treatment of minerals by the products of water electrolysis were studied using atomic force microscopy (AFM) and Diffuse Reflection Infrared Fourier Transform Infrared Spectroscopy (FTIR). It was determined that practically all types of treatment by electrochemically modified water (a product of non-diaphragmatic treatment, anolyte and catholyte) lead to an increase of surface roughness of the studied minerals due to formation of small rounded shape particles. In contrast to that, after treatment of chalcopyrite by anolyte, its surface becomes smoother. Various effects of treatment by the water electrolysis products on the adsorption of chemical and physical forms of butyl xanthate on the studied sulfides were established. As a result, the efficiency of the complex of AFM and FTIR methods, as one of the ex-situ approaches for monitoring the surface state of sulfide minerals and direct investigation of BKx adsorption products was demonstrated.INTRODUCTION In mineral processing, copper-zinc sulfide ores are one of the most complex products in view of their mineral composition, fine dissemination, complex inter-growth and the proximity of the technological characteristics of copper, zinc and iron sulfides. For the most complete disintegration, fine grinding of ores to a size of 0.074-0.044 mm is necessary. Consequently, the main method for processing of such ores is flotation, which bases on the difference in physical and chemical properties of the mineral surfaces, in particular, degree of wettability. The separation of copper and zinc minerals and their separation from ferrous and other sulfides, sulfosalts and rock mineral is a very difficult task (Chanturiya, 2000). For the successful separation of copper and zinc minerals in the appropriate selective concentrates, it is necessary to find conditions for the most complete liberation of ore and rock-forming minerals and for increase the contrast in physical and chemical properties of their surfaces. Despite significant progress in the processing of copper-zinc sulfide ores, the problem of the selectivity of the separation of the main ore minerals has not yet been fully solved and requires innovative approaches (Chanturiya, 2015). To date, various methods of preliminary energy processing of complex ores are used: magnetic pulse treatment, impact by high-voltage nanosecond pulses, electrochemical effects (including products of water electrolysis (Chanturiya et al., 2014; Bunin et al., 2015; Chanturiya et al., 2014a; Chanturiya et al., 2016), processing with flotation reagents, etc. Electrochemical treatment of water in various modes allows to obtain products of electrolysis with different oxidation-reduction properties: acid anolyte with a high oxidation potential and dissolved oxygen content, an alkaline catholyte with high reducing properties and a product of non-diaphragmatic treatment with enhanced reduction properties."

Jan 1, 2018

By Jacek Kolacz

"Comex has carried out an extensive research work related to optimising sensor based sorting systems. The main target was to achieve efficient separation and maintain high capacity of the process. Eventually, the operating cost of the sorting process was investigated in terms of potential industrial applications and possible replacement of the existing traditional processing equipment. The study included an influence of the following factors on the separation efficiency: capacity, particle size and distribution, particle shape, material properties like colour, density and composition, as well as percentage of the rejected fraction. The above factors were also considered in the calculation models for the operating cost of the sorting process. In addition, other elements were considered like compressed air cost, cost of energy, labour cost, and necessary service and maintenance cost. All these elements were implemented into the calculation model allowing quick and effective evaluation of the major parameters for sorting applications. Finally, the study was carried out for two popular sorting principles: visible light sorting utilising differences in color, texture and shape and X-ray sorting using differences in density and chemical composition. GENERAL INFORMATION ABOUT SORTING POSSIBILITIES Application of the sensor based sorting systems, without any doubt, brings a lot of possible advantages in many mineral operations. The main advantage of the new system is related to its universality and at the same time very sophisticated image processing functions, which can be carried out in the same processing unit (Kolacz, 2014). Figure 1 shows the CXR-1000 system from Comex with 1 m belt width, in the configuration where many different analysed parameters can be used to provide particle separation. The image analysis system includes a camera installed either over the transport belt conveyor or at its discharge end. The system includes the X-ray attenuation analysis realized by the XRT system in the central part of the conveyor belt. The sorting system can be used with both optical and XRT analysis or separately depending on an application."

Jan 1, 2018

By Wang Xu, Tao Dongping, Zhang Jie, Tao Youjun

Based on the principle of fly ash triboelectrification, the mineral electrical index and testing method are introduced. The electric differences of various mineral components of fly ash are discussed in view of the results of chemical and mineral composition analysis of the fly ash sample acquired from the Xin-wen power plant. The dielectric constant and charge-mass ratio of carbon and ash in the fly ash are determined. The data were then used along with the rotary triboelectrostatic separator (RTS) testing results to investigate the charging characteristic of fly ash particles in different sizes. The results show that the dielectric constant of fly ash with different particle size decreased with the decrease in particle size, which led to a poor electrical conductivity. Thus particle size has an important effect on conductivity. The charges of carbon and ash particles increased with decreasing particle size. The charge-mass ratio of carbon and ash particles of the same size increased with decreasing particle size. This indicates that finer particle size is more favorable for triboelectrification separation from the charging efficiency point of view. The rotary triboelectrostatic fly ash separation tests show that the best decarbonization performance was achieved with particles in the size range of 0.038-0.074mm with which the decarbonization rate and efficiency index reached 38.93% and 120.83% spectively.

Jan 1, 2014

By E. Scheepers

Within a phosphorus producing submerged arc furnace it was found that the continuous fluctuation of the furnace between a flowrate-driven state (high throughput) and a thermodynamic-driven state (low throughput) caused both techniques to have similar overall, predictive abilities and resulted in a linear, ARX-type, adaptive prediction model as the model of choice. Secondly, this pre-diction model was developed, tested and then shown to have a reasonable, 8-hour-ahead predictive accuracy (R2, coefficient of determination) of 30% (±6%) on future Pslag values. This inherent relationship exists because, at the precise moment of a Pslag prediction, the furnace already contains the metallurgical memory (input variables to the linear model) needed to ensure that some predictive possibilities will always exists - all as a result of the long residence times in the furnace. Residence time, however, is not a directly adjustable variable but rather a fully dependent variable and a function of an array of interconnected and interactive variables. In fact, this applies to virtually all input variables, reemphasising the importance of innate metallurgical memory. Thirdly, predictive control possibilities were explored by simulating the set-points of two fully independent variables used by operators to control the process: the ratio of fixed carbon-to-P2O5 and the ratio of silica gravel-to-pellets. This linear, predictive control model showed only a slight improvement with an 8-hour-ahead predictive accuracy of 35% (±7%). This highlights how ineffective current adjustments are in optimally steering the process and how difficult even incremental improvements in feed-forward and predictive control can be. Finally, it is shown that fundamental design-, sampling- and process restrictions currently associated with the process will always limit the predictive and especially control accuracy or meaningfulness of any dynamic model. These restrictions include the size of the furnace resulting in long residence times, 8-hours sampling intervals, an extremely complex and interactive process and a 16% spatial analyses variation on the Pslag values ? the very value that the model is to predict. The point is made that, given the current status quo, even the perfect dynamic prediction model can not improve on an 8-hour-ahead prediction of 30% (±6%). This barrier can only be pierced with e.g. tidier and more frequent sampling regimes and other upfront capital investments, a decision that becomes a cost accounting exercise and that can only be taken by the management structure. An investment demanding ever-increasing attention is CFD software and it?s potential to shed more light on the complex interactions within the furnace.

Jan 1, 2014

By L. S. Zhou

Germany-made AFX-100 multi-grade fluidized classifier, with exquisite built-in structure and unique novel design, materializes not only advanced and efficient classification, but also precise particle distribution and safe operation, in addition to lower energy consumption and operational cost. It, simultaneously in place of screw grader, water cyclone, and fine mesh sieve, is equipped with multi-function, and indicates superior advantage in comparison with other else grading facilities. As the third-generation equipment, which is efficient and modern, it, in China and therefore all over the world, will find wide application in processing both fine and ultra-fine iron ore resources. Industrial test, carried out in Benxi Steel?s Waitoushan Iron Mine, shows efficient classification, i.e., ?74µm particle contents in coarse, medium and fine products come to 6.09%,11.82% and 82.73%, respectively, while qualitative and quantitative efficiencies end up by 74.38% and 87.66%, respectively. Its separation efficiencies amount to 2.2 times as many as spiral classifiers, 1.8 times as hydrocyclones, and 1.3 times as vibration high-frequency fine screens. Another industrial test, which was practiced in Anshan Steel?s Donganshan Sinter Plant, indicates that classification qualitative efficiency comes to 65.06%, equal to 1.51 times as many as hydrocyclones; yield, 55.79%; -71µm particle contents in medium and coarse products, 42.02%; -71µm content in fine product, 95.42%; and concentration, 12.33%. Estimated separation indexes are as follows: Yield for concentrate at 31.22%, up 0.22% than that from general processing line; concentrate grade at 66.42%, up 1.13%; recovery ratio comes to 65.84%, up 1.28%, which, based on pilot study, results in 20 million yuan of economic return for Donganshan Floatation Plant.

Jan 1, 2014

By J. H. Zhang

An atomic force microscope has been used to measure the forces acting between two silica and two rutile surfaces in the presence and absence of cationic surfactants, CnTACl (n = 12~18). The forces measured in the absence of surfactant can be fitted to the DLVO theory. At short separations, however, the silica surfaces exhibited repulsive hydration forces, while the rutile surfaces did not. On the other hand, the forces measured in the presence of the cationic surfactants show long-range attractions that are larger than the van der Waals forces. The long range attractions are the strongest at of the point of charge neutralization (p.c.n.), which decreases with increasing surfactant chain length. The possible origin of the long-range attraction has been tested in view of the charged-patch model of Miklavic et al. (1994). However, the sizes of the patches back-calculated from the model were much larger than those the patches (or hemi-micelles) determined experimentally and reported in the literature. It is, therefore, suggested that the long-range attractions observed in the present work are due to the structural response of the water molecules in the vicinity of hydrophobic surfaces.

Jan 1, 2014

By Ricardo Montero

At this time, over 300 tons of Au are used in electronic equipment each year with other precious and strategic metals such as Ag, Pt, Pd, Cu, Nb, Ta, etc. After the use-phase, the electronic devices become electronic waste (e-waste); consequently it is important to consider e-waste as a secondary supply for recovery of these metals. One of the most important components is the printed circuit boards (PCBs) because the amount of their precious metals is ten times higher than rich precious metals bearing ore. This paper presents the recovery of Au, Ag, Cu and Nb from PCBs of discarded computers using leaching column technique. The amount of these metals in used PCBs was: 613 g/ton of Au, 1515 g/ton of Ag, 36 g/ton of Nb and 23.4 % of Cu. The PCBs were crushed with a hammer mill until reaching a particle size between 3.33 mm to 0.43 mm. Then, it was leached with sodium cyanide solution in a glass column using the following conditions: sodium cyanide concentration 4 g/L, flux 20 L/kg PCBs day, pH between 10.5 to 11 and leaching time 15 days. Every day, after leaching, the pregnant solutions passed through a column with activated carbon to complete the closed loop system. The following recoveries were obtained: 46.6% of Au, 51.3% of Ag, 47.2% of Nb and 62.3 % of Cu. The products obtained are: a) loaded carbon that contains the desired metals and b) processed PCBs with precious metal contents. A preliminary technical-economic study shows the feasibility to create a small-scale PCBs recycling plant. The initial investment is on the order of US$ 155 639, considering the recovered metals from loaded carbon. The internal rate of return for 10 years period (IRR) and net present value (NPV) estimated are 27% and US$ 105 926 respectively. Keywords: printed circuit boards, recovery, precious metals, niobium, leaching column

Sep 1, 2012

By Jacqueline Satur, Yoshiaki Kon, Buenaventurada Calabia, Xiao Sheng Yang, Arvo Naumanen, Kenzo Sanematsu, Sayaka Morita, Tetsuichi Takagi

Granite ores are composed of silicate minerals and a variety of valuable REE (rare earth elements)-bearing minerals, however the processing technique to recover these valuable minerals is not yet developed. In this study, the recovery of REE-bearing minerals by dry magnetic separation and wet high intensity magnetic separation (WHIMS)-settling from surface sample and from drill core sample, respectively, of a granitic REE-Zr-Nb ore deposit was investigated. The two samples have different mineralogy however in both samples, light REE are commonly contained in REE carbonate minerals while Y and heavy REE are commonly contained in zirconium silicate minerals and pyrochlore. The liberation size of the REE-bearing minerals in the two samples ranges from 10-250 ?m. Previous flotation testwork conducted on the drill core sample reported high recoveries of La2O3 (88%) and Ce2O3 (88%) but low recoveries of Y2O3 (42%), ZrO2 (17%), and Nb2O5 (29%). The objective of this study was to obtain higher recoveries of Y2O3, ZrO2, and Nb2O5 by dry magnetic separation and WHIMS-settling. Both processes implemented the application of a low magnetic intensity to initially separate the ferromagnetic minerals then a high magnetic intensity to recover the REE-bearing minerals. The results showed higher recoveries of Y2O3, ZrO2, and Nb2O5 by dry magnetic separation and WHIMS-settling indicating the potential of magnetic separation and gravity separation in recovering the heavy REE-bearing minerals. WHIMS-settling is more recommendable than dry magnetic separation because of its applicability in treating a wider range of particle size. In the WHIMS-settling, the light REE, Y, and Zr minerals were recovered mainly by applying four stages at high magnetic intensity of 21,500 gauss while the weakly magnetic pyrochlore was recovered mainly by decantation of the nonmagnetic slurry after a short settling time of 0.25 to 0.50 h. (MAX.300 words)

Jan 1, 2014

By Ljudmil S. Grigorov, Eric Forssberg, Hanumantha Rao Kota, Robert J. Pugh, Lidia B. Alexandrova

"We have used the microscopic thin balance developed by Scheludko at al. (1970) technique to study the stability and interactions within the thin film between the silica surface and air bubble with (i) a long chain C10 amine and (ii) a cationic/anionic surfactant systems consisting of mixtures of a long straight C10 chain amine with long straight chain C8, C10 and C12 sulfonates. It was found that the mixed surfactants caused lower contact angles, lower rates of the thin aqueous film rupture and longer film lifetime, compared to the pure amine system.This behavior was explained by the initial strong adsorption of positively charged interfacial complexes from the mixed surfactant system at the air/solution interface followed by adsorption at the silica interface. It was also shown that the chain length compatibility between the anionic and cationic surfactants controls the strength of the interfacial complex, determining an inhibition in the thin film rupture and dewetting of the film. The rupture mechanism was explained by an earlier established heterocoagulation mechanism between the positively charged air/solution interface and the solution/silica interface which remained negatively charged. The formation of the interfacial complex at the air/solution interface was confirmed by using surface tension data."

Jan 1, 2003

By Sushanta Majumder

The physico-chemical characteristics of raw materials used for the production of iron ore pellets have a strong influence on the productivity of pelletization operations and on the quality of pellets. Since iron ores from different sources are used for making iron ore pellets and since the quality of the ores varies with time, there is a need to optimize and control pellet plant operations on a regular basis to achieve optimum productivity while maintaining pellet quality within the desirable specifications. In order to achieve this objective, a model-based on-line optimization system was implemented on two industrial scale induration furnaces. The optimization system consists of a rigorous mathematical model of the induration process, a model for the permeability of the bed of pellets, a statistical model for the quality of iron ore pellets and an optimization module based on sequential quadratic programming. The rigorous model is tested on-line using the wind-box temperature available real-time. The process was optimized to enhance induration furnace productivity for the given constraints on pellet quality parameters such as the cold compressive strength (CCS) and Tumble Index (TI), and other equipment design parameters. Process variables such as induration machine speed, cold air flow rate and hood temperature profile were used as the optimization variables. The on-line optimization system was successfully implemented in two industrial induration furnaces and lead to enhanced productivity. Details of the on-line optimization system and results of process optimization will be presented.

Sep 1, 2012

By Fedotov. K. V., A. Y. Senchenko, V. A. Chanturiya

"The paper describes an efficient process to treat the ore from the largest in Russia copper deposit – Udokan. The recommended process is universally applicable to Udokan ores different in composition and allows reaching high copper recoveries during production of high-grade cathode copper and sulphide concentrate with 45% copper content. There are several promising trends for the process optimization and in the case they are implemented, economics of the whole project could improve significantly. One of the most important optimization options implies reduction of specific energy consumption in the course of comminution operations. Another possible option to optimize the already selected process flowsheet is production of cathode copper from sulphide concentrate directly at a mining and metallurgical plant without sending the latter to other metallurgical works.INTRODUCTIONUdokan copper deposit with resources of more than 20 million tons of copper is the largest in Russia and one of the largest copper deposits in the world. The deposit is located in Kalar District of the Trans-Baikal Territory, 30 km away from Novaya Chara railway station of the Baikal-Amur Mainline.Scientists and engineers from various research institutions have studied Udokan copper ores for years. Along the way, some conceptual process flowsheets have been proposed and each of them has its own pros and cons. The key requirement to the processes being developed was their universal application for processing of all the ore types using a single flowsheet. Due to the hard mining and geological conditions and because of complex material composition of Udokan ores it is of great difficulty to design a process which would provide for maximum economic benefits. That is why the process optimization has been ongoing until now.According to the Russian standards, the main input document for design of a metallurgical plant is referred to as a Process Design Report that covers the following key data sections: analysis of metallurgical testing results, validation of the process, design criteria, process flow diagrams, the mass and metallurgical balances, process description, equipment list and other information necessary for the subsequent design."

Jan 1, 2018

By N. Dhawan

In the last decades, High Pressure Grinding Roll (HPGR) has gained significant importance in hard rock processing due to numerous metallurgical benefits such as energy savings, particle weakening, preferential damage of coarse particles, and preferential comminution-liberation. There are a limited numbers of lab-scale HPGR units throughout the world. The laboratory-scale HPGR machine at the University of Utah is first-ever lab-scale machine designed by late Dr Klaus Schönert, the inventor of HPGR. This HPGR is constructed with two counter-rotating hardened tool steel rolls, each 200 mm in diameter and 100 mm in width. The HPGR unit is equipped with eight sensors and a robust control system, which serves as an ideal system for fundamental studies and lab-scale testing. In HPGR operation, throughput, energy and product size distribution are intricately linked to specific grinding pressure, roll gap and rolls speed. The nip angle existing during the operation determines the volume of feed material above the rolls that is pulled into rolls without slip. In this paper, scale-up factors and some of the existing models have been reviewed. A number of experiments have been carried out with limestone and a slag material. The influence of operating variables and their complex relationship has been studied.

Sep 1, 2012

By Shen Zhengchang

Based on the flotation features of coarse particle mineral, a new type of impeller & stator unit is developed. Particles suspension state generated by this impeller & stator unit under different speeds are tested in laboratory, and critical impeller speed suit for coarse particles flotation is presented. Comparing particle suspension parameters of the new impeller & stator unit with that of KYF impeller and stator unit, it comes up that the distance between the interface of two slurry circulation channels and the cell bottom is larger in the flotation cell with new impeller & stator unit. The test results indicate that the new type of impeller & stator unit is suitable for processing coarse particles due to its good suspension capacity for coarse particles. Keywords: coarse particles, flotation, suspension, critical speed, impeller and stator unit

Sep 1, 2012

By Caroline Olsen

The objective of this study was to achieve Zn activation control in an industrial Cu flotation circuit treating a complex Cu-Pb-Zn-Au-Ag sulphide ore at the LaRonde Division of Agnico-Eagle Mines Limited (Québec, Canada). In order to provide process relevant results, a laboratory testing methodology was developed to duplicate plant operational parameters. The action mechanisms of ZnSO4, TETA (triethylenetetramine) and NaHSO3used as depressants in order to limit ZnS activation were examined. Laboratory flotation tests with and without Cu2+ions (the ions responsible for ZnSactivation)were performed. All depressants showed equal or better flotation performance relative to baseline tests. For example, in the presence of Cu2+, the Zn recovery reduced from 32.2% to 17.5% in the copper rougher concentrate after adding ZnSO4(with a dosage of 50 g/t). TOF-SIMS analyses confirmed the relative decrease in surface Cu in the samples treated with ZnSO4and TETA. For the case with TETA, this indirectlyindicates the formation of a copper TETA complex in solution, thereby reducing available Cu for transfer. The TOF-SIMS and XPS data indicate that the addition of ZnSO4and NaHSO3resulted in an increase in surface metal hydroxides and SO3 on ZnS grains inhibiting both Cu and collector attachment.ZnSO4 was subsequently tested with success in the LaRonde concentrator. The addition of 40 g/t ZnSO4 at the conditioning (or cleaning) stage led to a 2% reduction in Zn content in the Cu and PM concentrate. Recently, improvements towards the control of copper sulfate addition in the downstream Zn flotation circuit resulted in the reduction of Cu2+ in process water. As this ?cleaner? water is recycled for Cu and PM flotation, the addition of ZnSO4 is now used only as required.

Sep 1, 2012

The ever increasing demand for energy and the progressive depletion of crude oil resources, have renewed interest in oil shale as an alternative fuel resource. Weathered oil shale samples were assembled from El-Nakheil phosphate mine in Quseir area, Eastern desert, Egypt. The oil shale samples were prepared and analyzed by XRD (X-ray diffraction), XRF (X-ray fluorescence spectrometry), and optical microscopic techniques. Rock-Eval pyrolysis and total organic carbon were used to study shale hydrocarbon potential. A leaching procedure using inorganic and organic acids was used to selectively dissolve the oil shale associated ash forming minerals. XRD results showed that calcite is the dominant carbonate mineral, whereas primary silicate minerals are quartz and montmorillonite. SEM (Scanning Electron Microscopy) observations indicated that the organic matter is dispersed throughout the rock matrix. The acid soluble fraction upon leaching was determined to be 37.59 and 42.74 wt% by using 5% HCl and 10% HCl, respectively. The TOC was increased from 20.78 to 29.88 and 34.09 wt% by using 5% HCl and 10% HCl, respectively. Keywords: el nakheil oil shale, characterization, xrd, xrf, sem, elemental analysis, proximate analysis, ultimate analysis, thin section, rock eval pyrolysis, acid leaching

Sep 1, 2012

The effect of the acid anion on chalcopyrite (CuFeS2) leaching has been examined, under care-fully controlled conditions, in a range of acids in stirred reactors and columns at pH 1. Solution speciation calculations were performed to determine possible rate controlling species. The relative leach rates of Cu from chalcopyrite can be explained quantitatively entirely on the basis of solution speciation without the need to invoke any rational relating to surface structure/speciation. The rate of Cu release is first order with respect to Fe3+ activity. The stirred batch reactor experiments at fixed pH 1, Eh of 750 mV (SHE) and 75? showed that chalcopyrite leach rates were rapid in both HClO4 and H2SO4 with 100 % Cu recovery after 73h and 97 h respectively. However, the leach rate in H2SO4 was slower as compared to the HClO4 leach due to a slower increase in the activity of Fe3+ due to the formation of FeSO4-. The presence of Cl- in the leaches (HCl and H2SO4 with NaCl added) led to a low activity of Fe3+, due to the high activity of FeCl2+, resulting in very low leach rates. For the column leach experiments dissolution of Fe and Cu from the pH 1 HCl eluted chalcopy-rite column with quartz proceeded at several times the rate of any other column (chalcopyrite with and without quartz and/or pyrite leached with H2SO4, HClO4, HCl). Three observations indicate that galvanic interactions are not leach rate controlling role: a) The rate of leaching was not uniformly increased for the non-quartz containing columns where the two sulfide minerals, chalcopyrite and pyrite, are in physical contact as compared to the analogous quartz containing columns where they are not; b) there exists a reasonable correlation between the rate of Cu release and the effluent Fe3+ activity for all columns thus indicating that the leach rate is determined by solution speciation; and c) in all cases the proportion of Fe to Cu leached indicates preferential dissolution of Cu over Fe. However, the proportion of Fe to Cu is either the same or greater than expected on the basis of the single mineral columns. This indicates that chalcopyrite is not dissolving preferentially to pyrite.

Jan 1, 2014

By H. R. Manouchehri

Large variations in flotation characteristics of minerals have been observed in winter and summer in plant practices as a result of changes in pulp temperature. Variations in temperature may affect the quality for pulp and related process water through changes in dissociation of different chemical species within the pulp, as well as changing in gas and metal hydroxide solubility, reagent adsorption and its stability on mineral surfaces, water/pulp viscosity, etc. All of these affect the flotation characteristics of specific mineral to some degree or another. It has been observed in Cu-Pb-Zn and/or Pb-Zn sulfides flotation that sphalerite (ZnS) flotation is strongly affected by changes in pulp temperature. Plant practices have shown that at the both low, e.g., T <10-12°C, and high, e.g., T > 60°C, the recovery for copper activated sphalerite is dramatically dropped. Within this paper the effect of pulp temperature on flotation characteristics of sphalerite is brought into considerations and laboratory flotation tests were conducted in conjunction with surface and solution chemistry analysis to understand the effect of temperature on sphalerite recovery. The effect of temperature seems to be complex since the temperature affects both the physical (hydrodynamics) and chemical phenomena in the flotation cell. In fact all sub-processes in flotation, i.e., collision, attachment and detachment, are affected by changing in temperature. Experimental results indicating that at alkaline pH values, e.g., 8.5 to 10.5, the recovery for copper-activated sphalerite is dramatically reduced when temperature is below 10-12°C, which is in agreement with plant practice at Boliden?s Garpenberg plant in Sweden. However, results from other studies indicated that the zinc recovery is also considerably decreased at high pulp temperatures, i.e., 62°C and above.

Sep 1, 2012