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By Andrei Kolesnikov

"The results of CFD modelling of complex heat transfer and fluid flow in DC electric arc furnace are presented. The model includes energy and momentum conservation equations for gas phase (freeboard), liquid phase (molten bath) and solid phase (walls and graphite electrode). Simulation revealed the temperature distribution in all elements of the furnace. The influence of the arc and melt resistance on the temperature distribution is discussed.Computational Fluid Dynamics (CFD) becomes a powerful tool for better understanding of the heta and mass transfer processes in industrial equipment. In current work commercial CFD software STAR-CD was used to analyse complex heat transfer in DC EAF, including forced and natural convection, conduction and radiation. The finite volume solver using body-fitted grid was used. The grids are non-staggered hexahedral grids and all variables are evaluated at cell centers. Steady-state calculations were performed with PISO algorithm. For the convective terms in equations the hybrid differencing scheme was used. An upwind differencing scheme was used for other terms. Conjugative heat transfer was taken into account in heat transfer calculations on gas-liquid and gas-solid interfaces. Radiation from the arc and inner surfaces of the furnace was calculated by a “discrete beam” approach. Source term in energy conservation equation was used to represent heat release in the zone occupied by the DC electric arc. The volume of this zone was calculated from semi-empirical equations. The Joule heat and heat due to chemical reaction in the melt were calculated through the source term expression in the energy balance equations for the slag and metal in the molten bath. The gas acceleration in the electric arc zone and stirring of the slag due to gas bubbles motion were accounted for by momentum source terms in the momentum conservation equations.All simulations were carried out using axisymmetric two-dimensional grid. The grid resolution was 20 cm per cell in most part of the furnace, except the arc region, where resolution was 5 mm per cell."

Jan 1, 2003

By R. Singh

The paper presents the results of characterization and beneficiation studies carried out on a lean grade tungsten ore sample from Degana, India. Basically, three different routes, involving gravity separation, magnetic separation, and froth flotation were studied for concentration of the sample by physical and physico-chemical methods. Considering the low recovery by physical methods, efforts were put in to produce a tungsten concentrate by physical methods suitable for subsequent hydrometallurgical recovery of tungsten as ammonium para-tungstate. This strategy proved quite helpful in minimizing the losses of tungsten in tailings. Based upon these studies a novel integrated technological process flow-sheet was developed for the exploitation of lean grade tungsten ore deposit of Degana, India. Keywords: lean tungsten ore, characterization, beneficiation, gravity and magnetic separation, hydrometallurgical extraction, integrated process route

Sep 1, 2012

By G. R. Forbes

Flotation froth machine vision systems provide consistent real-time measurements pertaining to the state of the flotation cell being monitored. Typical measurements include froth velocity, froth colour, froth texture and froth stability. This paper presents the results from test work conducted on the molybdenite rougher circuit at the Kennecott Utah Copper Concentrator during February 2006. Machine vision results show that it is not possible to accurately determine bubble size distribution information for the molybdenite froth, despite using state-of-the-art methods. Instead, it is necessary to make use of texture measurements to classify the various different froth states. Numerous combinations of texture measurements and classifiers are used to determine the best combination. Results show that the Fourier ring based texture measurements perform the best when both K nearest neighbour and Gaussian mixture model classifiers are used. The concentrate grade of the flotation cell is modelled using combinations of froth velocity and froth texture descriptors. The results show that by using a linear combination of these descriptors rather than either one by itself it is possible to account for a much larger percentage of the variation observed in the concentrate grade data. Adjusted R2 values of 92% and 84% are achieved when modelling the copper and the molybdenite concentrate grade respectively.

Jan 1, 2014

By T. Suzuki

Acid leach liquors from spent lithium-ion batteries employing lithium cobalt dioxide (LiCoO2) as a cathode active material contain valuable metals such as cobalt and lithium, as well as common metals such as aluminum and copper. The objective of this study was to develop a hydrometallurgical process providing a high selectively between aluminum, cobalt, copper, and lithium from hydrochloric acid solutions. Batch experiment results showed that selective hydroxide precipitation approach was not suitable because a significant amount of cobalt and lithium was co-precipitated with aluminum and copper hydroxides. In contrast, batch experiments and the subsequent data analysis indicated that the sequence of solvent extraction circuits using PC-88A, Acorga M5640, and tri-n-octylamine (TOA) extractants effectively separates four metals of interest. In the first circuit of the proposed process, copper was selectively extracted by Acorga M5640 at the pH 1.0-2.0. Aluminum, cobalt, and lithium remain in the aqueous phase. In the second circuit, aluminium is selectively extracted by PC-88A at pH 2.0-2.5. For the separation of remaining cobalt and lithium, Acorga M5640 provided higher separation efficiency compared to PC-88A single extractant and PC-88A/TOA mixed extractant. However, the stripping efficiency of cobalt from the Acorga M5640 organic phase was found to be low (less than 10 %). Therefore, PC-88A/TOA mixed extractant rather than Acorga M5640 is an advisable choice for the separation of cobalt and lithium. Keywords: spent lithium-ion secondary batteries, solvent extraction, lithium, cobalt

Sep 1, 2012

By S. Banisi, Seyyed Omid Mousavi, Alireza Ghasemi

Discrete Element Method (DEM) is extensively used to simulate the behaviour of particles in various processing units. This method is based on modelling the forces acting between particles in any contact and consequently calculating the new position of particles. The high number of elements and numerous equations needed have made the required computation time very long even using computers with very fast processors. The required computation time mainly depends on the time step. If the time step is chosen very short, the computation time will significantly increase. On the other hand, if the time step is chosen very long, the simulation will be in error due to not fully observing the contacts. In DEM calculations, the time step is chosen as a fraction of the collision time. In this research, a relationship was proposed between the contact time fraction and the error of simulation. In other words, to select the time step in addition to physical parameters, the accuracy of the simulation was also accommodated in the frequently-used relationships. The simulation error was defined as the relative difference between the initial restitution coefficient and the restitution coefficient obtained after simulation. The required time steps to arrive at the simulation error of 5% were calculated for two common contact force models namely, Hertz-Mindlin and linear spring-dashpot. The simulation was performed for two particles with radius of 3 cm, elasticity modulus of 210 GPa, Poisson's ratio of 0.3 and relative velocity of 0.5 m/s. The required time steps were found to be 2.3 and 0.19 µs for the Hertz-Mindlin and the linear spring-dashpot contact force models, respectively. Results showed that with a scaling-down the modulus from 210 GPa to 2.1 MPa, the required time steps for the Hertz-Mindlin and the linear spring-dashpot contact force models, with an equal simulation error, increased by 100 and 316 times, respectively.

Jan 1, 2014

By Kr. J. Dedelyanova

Selective flocculation of iron minerals could improve the economics of high intensity magnetic separation as concomitant process. When the minerals are finely disseminated is necessary a finer grinding to be applied which generates a lot of slimes. The HIMS is not enough efficient for particles below 20 microns ? territory where the selective flocculation is already well known industrial practice, so the combination of these two methods of beneficiation can bring a higher grade at high recovery to be achieved. The dynamics and selectivity of the precipitation process is studied in batch tests with flocculant starch and dispersants sodium silicate and sodium hexametaphosphate. The influence of preliminary conditioning with nitrogen acid at pH 2 before flocculation is also investigated. Flowsheet including these two methods is tested and the distribution of iron is shown.

Jan 1, 2014

By S. H. Morar

Froth stability is widely recognized as a key driver of flotation selectivity. It is well known that froth stability is affected by the type and quantity of surface active reagents present (frothers), and the concentration and hydrophobicity of solid particles present. While some studies have been performed on the effect of frothers on froth stability in three-phase systems and the hydrophobicity of particles present, very little work has been performed on the effect of solids loading on froth stability. This may be due to insufficiently robust measurement techniques. This paper investigates the use of a new machine vision measurement to measure solids loading, and the relationship between this measurement, bubble size, and bubble burst rate on the froth surface. Keywords: froth flotation, machine vision, solids loading

Sep 1, 2012

By V. F. Petrov

Today, sodium cyanide is extensively used for extracting gold, however it is highly toxic to the environment if not managed properly. This paper discusses the key challenges presented to gold operations in efforts to come into alignment with the Russian environmental regulations and suggests solutions to overcome these challenges. It is a fact that the major environmental threat cyanide poses to water sources. Therefore, natural water sources should be well protected from the adverse effect of cyanides used in hydrometallurgical processes. For this, the following site procedures and facilities are practiced: in-site and external water recycling systems, reclaim water treatment if required and tailings ponds with water impermeable screens (tailings ponds with controlled leakage). Cost comparison analysis of cyanide destruction methods was carried out. It was revealed that the aldehyde treatment method developed by Irgiredmet JSC demonstrated the best economics. Cyanide emissions are treated by mass-manufactured packed and membrane devices which allow to keep cyanides at the acceptable limiting values established by environmental regulatory agencies.

Jan 1, 2014

By Zoran M. Stevic, Mirjana M. Rajcic-Vujasinovic, Zvonimir D. Stankovic

"Covellite is one of the most important copper sulfide minerals. Its behavior during the anodic polarization, as well as its rest potential in various solutions are of importance for flotation processes and also define the mechanism of electrochemical extraction of copper from sulfide minerals.Measurements of the rest potential have been performed in water solutions in presence of different cations and anions. The existence of the Nernst type dependence of the rest potential on the activity of some of the investigated ions was established. The biggest influence on the rest potential of covellite exhibits the change of activities of the ions forming the crystal lattice of investigated mineral, i.e. Cu(II) and S(II). The dependence of the rest potential of covellite on logarithm of Cu(II) activity has a shape of a strait line with a positive slope of 60 mV, while when concentration of S(II) anions increases ten times, the rest potential of covellite decreases about 120 mV. The first dependence was established in acid medium, while the second was registered in alkali one.Different electrochemical techniques have been used for the investigation of the behavior of covellite during anodic polarization. In the basis of all these measurements is a three electrode system consisted of: 1) working electrode made of the sample of natural covellite from the Bor mine (Eastern Serbia, Yugoslavia); 2) reference electrode (saturated calomel electrode) and 3) counter electrode (flat platinum). Electrolyte solutions used in these investigations are of the same kind as those used in the rest potential measurements. Sulfate and chloride solutions, as well as the mixed sulfate/chloride solutions, are the most perspective from the application point of view.Cyclic voltammetry has been the first used method that confirmed the formation of passive layer on the electrode surface during anodic polarization. Elementary data about the reaction mechanism have been obtained too. More detailed data needed for more precise conclusions about the mechanism and rate of the anodic process on covellite have been obtained by galvanostatic method. It was established that the essential difference exists between the reaction mechanism in sulfate and chloride solutions. Also, the difference is exhibited in the nature of reaction product directly connected with the passivation of the electrode surface. Chronopotentiometric investigations have been performed in sulfate, nitrate, chloride perchlorate and mixed sulfate/chloride solutions applying different current densities. The shape of obtained curves indicate if there was a surface passivation and how intensive it was."

Jan 1, 2003

The Arctic is a region of special economic, geopolitical, research, socio-ethnic, and defense interests of both Russia and other countries of the Arctic zone. Introduction of innovation technologies at ore-processing factories is a direct responsibility of the state and this problem should be solved on the basis of coordination of interests of different stakeholders. The task of elaboration of scientific principles of rational state regulation in the North is very topical. Innovations require considerable investments first of all from private capital. However as an investment object innovations are not attractive for investors as they require large expenditures for long-term projects, and they are connected to high risks because market incentives form striving to get quick profits of private companies and result in a certain behaviour strategy while innovations need ?long money?. Under such conditions without state regulation of investment and innovation activities development of the mining sector in the Arctic practically has no prospects. At innovation development of mining enterprises economic growth is provided at the expense of active state innovation activities. The elaborated strategy of ore-processing enterprises should correspond to the modern paradigm of the ore-processing industry development which is not only for extraction of minerals but also for multi-profile structure having comprehensive use of the resources on the rational basis intended for rational complex utilization of mineral resources of the AZR which by the definition includes maximally full use of the whole aggregate of resources on the economically rational basis with obligatory environmental with resource reproductive and socio-economic functions and deterrents. The main principle of creation of innovation technologies is to obtain more products of higher quality with minimal costs. This allows increasing ?productivity of the resources? several times. This principle makes increasing productivity of the resources the most important and in this case efficiency of use of the resources brings extra profits at the expense of lack of new costs such as payment for protection and utilization of wastes. According to the economic theory only ratio between demand and supply is able to fix optimal proportions in economy and to give necessary signals for investment activities of mining enterprises. In this context market for minerals and increase of mineral resources productivity do not create incentives for investment activities without which neither sustainable economic growth nor solution of macroeconomic tasks are possible. Nevertheless countries should not reject this idea in spite of economic efficiency of the enterprises. Extraction degree of useful components and especially oil in the Arctic zone is one of the lowest in the world. This can lead to crisis of oil industry and other mining sectors. The reason for that is lack of a state policy of realization of innovation technologies in the mining sector in the Arctic.

Jan 1, 2014

By Güven Önal, Zeki Dogan, Neset Acarkan

"In general, the processing of glass sand may involve comminution, washing, wet classification and attrition scrubbing. Additional processes may include magnetic separation, flotation and leaching in various combinations.Yaliköy sand dune deposit is located near to Istanbul on the European side by the Black Sea coast. The reserve of deposit is around 70 million tons. Iron content of Yaliköy sand dunes is 0.48 % Fe2O3 and not suitable for glass manufacture. The iron content of glass sand should be less than 0.15 % Fe2O3 for window glass manufacture and 0.05 % Fe2O3 for glassware. In this study, it was aimed to produce glass sand with less than 0.15 % Fe2O3 for window glass and with less than 0.05% Fe2O3 for glassware manufacture from Yaliköy sand dunes. A representative sample with a weight of 200 kg was taken from Yaliköy sand dunes deposit through opening small pits.• Mineralogical studies have shown that iron is present in three forms:• Hematite, limonite, clay and iron silicate minerals such as epidote and garnet occur in free form.• Quartz grains are coated by hematite and limonite.• Iron is also present in the cracks of quartz grains.Free iron minerals such as hematite and limonite and silicate minerals were subjected to magnetic separation and flotation for removal. Iron coatings were tried to be removed by scrubbing and leaching. Iron removal in the cracks of quartz grains was attempted by grinding and leaching.Under optimal conditions, sand concentrate with 0.38 % Fe2O3 was obtained by means of high intensity disc type magnetic separation. Grinding and scrubbing were applied to see the effect of size reduction and attrition at room temperature and 90 ºC, by using non-magnetic fraction. Sand concentrate with 0.13% Fe2O3 was obtained at 90 ºC in this test.Sand sample which was previously ground to minus 0.5 mm and scrubbed, was floated by using sulphonates as collector. After flotation tests, sand Concentrate was obtained with 0.11 % Fe2O3.The optimum iron removal was achieved by H2SO4 leaching at 90 ºC depending on acid concentration and leach duration in static, percolation and agitation leaching. Agitation leaching was done by the use of mixer at 600 rpm, 50% solids and leach duration was 15 minutes."

Jan 1, 2003

By Hemant Nerurkar

The destination of human development journey is envisioned as human well being. Human well-being is the extent to which individual share the ability and the opportunity to live the kinds of lives they value it includes environmental security, good health and living conditions, all of which are closely related to each other. The breakthroughs, which transformed the human race, have close interdependency with the environment. With the increase in world population, the requirement of natural resources is increasing every day. The nature is still stronger than man is but we must use natural resources more responsibly. The key to our well being is sustainable development Development effort for human well being may have adverse impact on the environment also. To keep the net impact positive is critical for sustainable development. For mineral processing industry, the value of a mineral is in the actual value as perceived by the end user. The process designs, investments in technology development all have direct relationship with the value of use and making a net positive impact on our ecosystem The value proposition has shifted towards raw materials and is a big differentiator. The availability of good quality raw material is difficult or is available at a premium. The challenge today is to develop green technologies that make effective and efficient usage of low grade raw materials The low grade raw materials as available pose a significant opportunity for human race for delivering value. They offer an easier reach to a value as perceived in end use but the journey is full of challenges. The first challenge is development of technology for maximizing grade recovery as required by the downstream process. The second challenge is to make the technology viable so that it contributes value to end use and the third challenge is to keep the net impact of the process positive The mining and mineral processing fraternity, being at the beginning of this value chain is set to take the first step in this journey for a tryst with ultimate human well being. Keywords: sustainable development, challenges in mineral processing

Sep 1, 2012

By Yuexin Han

The wet preconcentration of haematite, comminuted by high-pressure grinding roller was studied, using the cylindrical ferromagnetic medium. The effects of various factors including rod diameter, rod gap and background magnetic field intensity (BMFI) on the performances of preconcentration for different size fractions and the force analysis of single mineral particles with different diameter in the separation zone were emphatically investigated. The results showed that as the rod diameter increased, the rod gap decreased, and the BMFI increased the tailings grade and the tailings yield reduced while the concentrates recovery raised that was regardless of variations in feed size distribution. For the -3.2+0.18mm size fraction preconcentration, the magnetic medium with a rod diameter of 4 mm and a rod gap of 7 mm at BMFI of 454kA/m is used to get a higher performance. For -0.18mm size fraction preconcentration, the magnetic medium with a rod diameter of 4 mm and a rod gap of 4 mm at BMFI of 263kA/m is used to get a higher performance. After the classifying preconcentration, at the optimum condition, the overall concentrate grade increases by 9.56 percentage points and the concentrate recovery is up to the 82.67% with a tailing grade of 10.68% and a tailing yield of 40.31%. The magnetic force, exerted on weekly magnetic minerals was proportional, to the specific susceptibility and square of BMFI. For the same BMFI, the magnetic capturing force on coarse particles increased, and that on fine particles decreased with the increasing of rod diameter. For the lean locked-particles, considering the gravity and viscous resistance of particles, rods with a big diameter were beneficial to the capture of coarse particles and had no influence on the capture of fine particles, while rods with a small diameter were good for the capture of fine particles and not suitable for the capture of coarse particles of lean locked-particles. Keywords: low grade haematite, high-pressure grinding roller, high intensity magnetic separation, pre-concentration

Sep 1, 2012

By Rogerio C. Guimarães, Antonio E. C. Peres

The production of phosphate concentrates (phosphate rock) from slimes represents a challenge to the phosphate industry worldwide. In Brazil, this challenge is particularly relevant due to the consistently low P2O5 grades and the igneous origin. The first industrial experiences of producing phosphate rock from slimes (-44µm or -325#) fraction started at Arafertil, currently Bunge Fertilizantes SA, in Araxá, in the 1980.s. This production corresponds, nowadays, to 35% of the total production of concentrates in the company (830,000t/year) in a circuit consisting of desliming in 40mm microcyclones and concentration in flotation columns, corn starch and fatty acids being utilised as reagents. The performance of slimes flotation and the process control, at Bunge´s concentrator, were improved after the introduction of column flotation technology, in the first half of the nineties. The column flotation technology for slimes recovery was expanded to other Brazilian concentrators still in the nineties: Ultrafértil (Catalão - GO), Bunge (Cajati - SP), Fosfértil (Tapira - MG) and Copebrás (Catalão - GO). At present the Brazilian production of phosphate rock is approximately 4.5Mt/year, with a strong trend for a market increase. Genuinely Brazilian technology is utilised for the processing of slimes, the concentrates representing 11 to 13% of the overall production. The production of apatite concentrates from slimes was relevant to increase phosphate recovery and reduce costs, contributing to the growth of the fertilisers industry.

Jan 1, 2003

By R. Van Hille, S. Lacour, A. E. Lewis, K. Peterson

"This paper compares thermodynamic modelling results with those obtained for copper sulphide removal from aqueous solution in both continuous and batch experiments at laboratory scale. Sulphide precipitation has been demonstrated to be an effective method for heavy metal removal. The advantages are the high degree of metal removal at low pH, low quantities of sludge formation, the ease of de-watering and low reactor retention time due to high reactivity of sulphides. However, the low solubility of sulphide species can lead to spontaneous nucleation of fines, which are difficult to remove.Theoretical modelling was carried out using ASPEN Plus™ and OLI systems Inc ESP process. Both simulators were used to calculate copper sulphide recovery and residual aqueous copper concentrations as a function of pH. The predictions were then compared with experimental results. Both simulations predicted that all of the inlet copper would precipitate as sulphide CuS(s) over the entire range of pH and sulphide: copper molar ratios investigated. The simulation results were strongly influenced by the number of chemical species and the nature of the thermodynamic data taken into account in the model.The continuous experimental studies were carried out in a fluidised bed reactor (FBR). Copper sulphate was reacted with sodium sulphide and the solid precipitated directly onto the pellets in the FBR. The use of sulphide was motivated by high sulphate levels in local acid mine drainage and the ultimate integration of the metal removal process with a biological sulphate reducing process that produces an aqueous sulphide stream.A maximum dissolved copper removal of 99.6% (AAS analysis) and a total removal efficiency of 95.8% (dissolved copper minus fines) were achieved. Stoichiometry of the precipitate was determined from SEM/EDAX analysis (atomic percentages) and was close to 1/1, irrespective of the operating conditions."

Jan 1, 2003

The present work aimed to verify the possibility of using froth flotation to separate the constitu-ent minerals of an alaskite rock waste having as the main minerals quartz and feldspar. Three stages of tests have been carried through. In the first stage was used an amphoteric collector for flotation, diaminedioleate, at pH 2 and, after analyzing the final products, a very poor selectivity was ob-served. During the second stage of tests, different collectors that are normally used for feldspar flo-tation as amines, sulfonates and soybean oil were employed. Once more, it was not possible to reach reasonably selective results. In the third stage, a salt of etheramine was used for collecting the feldspar and hydrofluoric acid was utilized for controlling the pH. A simulation of three flotation steps (rougher, cleaner and recleaner) permitted to attain a good selectivity in the flotation process. A concentrate with a silica content of 96.6% was obtained. The low concentrate content of alkalis totalizing 0.52% and a feldspar recovery of 96.5% to the tailings, represented by the high content of Na, K, and Al2O3 in the tailings, demonstrated that the concentrate was made up mostly of quartz.

Jan 1, 2014

By Markus A. Reuter, Jacques J. Eksteen

"The modelling of bath type furnaces tends to be either fundamental in nature or total empirical ""black box models"". While models of the first kind are robust, they tend to lack accuracy, in cases where they are to be used for process control, and may take an overly long in development time. On the other hand, black box models tend to lack robustness of prediction for all circumstances and tend to be limited to interpolate based on historical data. While this may very often provide short-term accuracy, the models may have problems with stability in the long term. Moreover, the model structure may not reflect any of the fundamental properties of the system and remains opaque to fundamental analysis. The aim of the model development is in obtaining a model that have robustness, high accuracy, a short development time and which is adaptive to a changing environment. The models are specifically developed for on-line decision support or control of furnaces. The modelling approach is evaluated for a chromite bath smelting furnace. The role of systems analysis, mass balance smoothing, thermodynamic analysis are integrated into one generic algorithm for bath type furnaces. Not only are fundamental process relationships such the mass and energy balances satisfied through a scientific method of data reconciliation; the proposed modelling approach allows adaptive prediction, the first step towards predictive control or metallurgical decision support.It is shown that neither an ARMAX model only, nor a purely equilibrium model only, could predict the dynamics of the process very well. However, a combination of the two approaches more than doubled the accuracy as measured by the R2. It was noted for carbon dissolved in the alloy, that the improvement in R2 in using a hybrid modelling approach was more than the sum of the R2 of the individual traditional approaches. Similar improvements in modelling performance were noted for all other species.It shows further that process dynamics may totally overshadow the effect of thermochemical equilibrium (even when the thermochemical equilibrium prediction includes the recycled alloy and slag heels as additional feeds). The exclusion of process dynamics therefore leads to erroneous results."

Jan 1, 2003

By E. V. Bratygin, S. P. Elnikova

"In the article carrying out technique of experiments for estimation of power efficiency of process of crushing in cone crushers «in a layer». The conformity of the granulometric characteristics of the crushed products obtained as a result of the tests, the theoretical equations for the size characteristics, and the choice of the optimal equation for the prediction of the granulometric characteristics of the final products obtained by crushing ""in a layer"". Optimization of granulometric composition of power of crushers working ""in a layer"" is carried out with the purpose of reduction of the electric power consumption at reception of a product of required quality. As a result of the experiments, dependencies are obtained, the relevance and applicability of the crushing process ""in the layer"" for obtaining crushed stone of improved quality is proved. INTRODUCTION A number of equations have been proposed for calculating the breakage energy. These include equations by Kirpichev and Kick, Rittinger and Bond (Bogdanov, Olevsky, 1982). Another equation for calculating the specific breakage work in breakage by impact and in stratum was proposed by Devyatkin (Boiko, 2003). In these equations, the breakage energy is proportional to the particle size raised to some power. In the equation proposed by Devyatkin, the ore piece thickness or the feed average diameter is used. The relationship between energy and breakage can be expressed as an equation (Lynch, 1981; Tikhonov, no. 3, 2008) where k is a coefficient characterizing the energy parameter depending on the strength of the feed, l is size in microns. The Rittinger formula is obtained for n = 2, the Kirpichev-Kick formula for n = 1, the Bond formula for n = 1.5. For n = 3 or higher, the equation describes fine and ultrafine grinding. R. Hookey proposed a formula (Lynch, 1981, Tikhonov, no. 3, 2008), where the size exponent n is substituted by a size function In all of the above equations, a single value of the feed and product size is used; for example, in the Bond equation, size is defined as the particle size of the 20% oversize (P80 and F80). However, a single size value can represent multiple distributions, making that the Bond method inappropriate for determining the size (Lynch, 1981). Describing an equation for estimating the grinding energy will allow to design the electric drive and ore preparation circuit for the given breakage method."

Jan 1, 2018

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

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

Jan 1, 2003

By Yang Zhao, Tao Xiu-xiang, Chen Song-jiang

"China is rich in low-rank coals that account for 45.68% of existing coal reserves in China. The clean and efficient utilization of low rank coals is of great significance for ensuring the effective energy supply and promoting economic development and environmental protection. In order to solve the difficult problem in flotation of low rank coal, it has become the focus of research in the related field that oily bubbles instead of air bubbles are taken as a carrier in flotation to improve the attachment efficiency and recovery of low rank coal. In this paper, low rank coal slime collected from Shendong mining area was used as the experimental material, and it focused on the characteristics of oily-bubble flotation process of low rank coal. Additionally, difference in conventional flotation and oily-bubble flotation was discussed. The induction time between air bubbles, oily-bubbles and fine low rank coal particles was measured. The results indicated that the induction time between oily-bubbles and coal particles was obviously lower than that of air bubbles. By comparing the foam height of air and oily bubbles, it was found that the amount of oily bubbles is less than air bubbles, causing relative low flotation rate of oily-bubble flotation at initial stage. Besides, the maximum foam height and half-life of air bubbles and oily-bubbles were measured respectively. The results showed that the stability of oily-bubbles was higher than that of air bubbles, which is benefit for the enrichment of concentrates. The clean coal water recovery of oily-bubble flotation is lower than that of air bubble flotation, which indicated oily-bubble flotation is lower in water entrainment. INTRODUCTION China is the largest energy consumer in the world, accounting for 23% of global energy consumption in 2016 and 27% of global energy consumption growth. Whereas coal is taken as the major primary energy source and its share of China’s primary energy consumption is 62% in 2016, in which the low rank coals, such as lignite, long-flame coal, weakly caking coal, and non-caking coal, accounted for about 50% of total coal production capacity (China’s energy market in 2016, BP). Moreover, the exploitation and utilization of low rank coals and other coals that are difficult to float have been an important strategy for China’s sustainable development of the coal industry (Liu et al., 2014). However, the combustion of low-quality coals leads to a serious environmental pollution. In addition, the deterioration in geological conditions of coal resources, and the increasing improvement in the mechanization for mining significantly caused the increased amount of fine coal."

Jan 1, 2018