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By Ibrahim Alp, Duygu Dinç, Ersin Yazici, Adularya Energy and Electricity Generation and Mining Inc., Oktay Celep, Haci Deveci

Thiosulfate leaching as an environmentally benign alternative to cyanide leaching has received particular attention in recent years. Most studies have focused on thiosulfate leaching of free milling ores and, to some extent, pregrobbing ores. In this study, leaching of gold from the refractory Kaletas ore (in which gold/silver alloy is the only mode of occurrence detected) in ammoniacal thiosulfate solutions was studied. A two-level full factorial design (23) was adopted to investigate the effects of concentration of thiosulfate (0.2-1 M Na2S2O3), ammonia (0.5-1 M NH3) and copper (0.05-0.1 M CuSO4) on the extraction of gold from a ground ore (-38 µm) over a period of 24 h. Statistical analysis confirmed the leaching of gold improved with increasing concentrations of thiosulfate and ammonia. In contrast, increasing the concentration of copper in the range tested adversely affected the extraction of gold. The magnitude of effects of parameters on the gold extraction was in the order of Na2S2O3 > NH3 > CuSO4. The maximum extraction of gold (69.6%) was obtained in the presence of 1 M Na2S2O3, 1 M NH3 and 0.05 M CuSO4. The negative influence of copper on gold extraction is most likely attributed to the decomposition of thiosulfate catalyzed by copper. Concentration of thiosulfate was also identified to be statistically the most important parameter for its consumption.

Jan 1, 2014

By H. J. Liang

In this study, zeta potential and contact angle measurements of pyrite before and after interacting with Thiobacillus ferrooxidans are carried out to investigate the changes in its surface properties. The results show that, after pyrite interacting with Thiobacillus ferrooxidans and its metabolite, the surface electricity of pyrite changes obviously, resulting in a notable shifting of isoelectric point to lower pH value, but the contact angle varies little. Bacterial protein plays the most important role in the interaction. This work is helpful to disclose the mechanisms of Thiobacillus ferrooxidans de-pressing pyrite flotability.

Jan 1, 2014

By Alejandro Rubio-Lopetegui, Gonzalo Montes-Atenas

The occurrence of Enargite (Cu3AsS4) in hydrometallurgical plants bears a number of challenges. One question lies on how Copper and Arsenic can be selectively extracted from the solid surface structure when immersed in aqueous solution. The leaching of Enargite in ambient conditions has been extensively studied; nevertheless, challenges regarding the process kinetics and surface structures enabling the extraction process remain ill-understood. Prior knowledge indicates that different conditions of pH, Eh, temperature, speciation of the aqueous phase or variations of these parameters defines the overall rate at which metals and other elements will be transferred to the solution. One aspect that the research studies have seldom addressed involves studying the main features of the surface structures formed during the leaching process at the outmost surface atomic layer. Such structures will mediate between the solid bulk and the solution to undertake subsequent stages of leaching process. The aim of this research work is to critically analyze the state of the art of Enargite electrochemistry from the mediator formation-dissolution mechanisms standpoint occurring at the mineral-solution interface. The most probable mediator species reported in the literature were found to be: Arsenolite and Sulfur (acidic media), Covellite (acidic and alkaline media) and Tenorite (alkaline media). As a result of this analysis, it was observed that the surface speciation was not in full agreement with the previous knowledge suggested to explain Enargite leaching reactions and, therefore, modified Eh-pH diagrams are presented. The acquired insights on the surface structures rising from the Enargite-aqueous solution interactions is further revised to provide new experimental protocols towards selectively separating Copper and Arsenic through hydrometallurgical paths.

Jan 1, 2014

By Andrzej Luszczkiewicz, Alicja Bakalarz

The application of new collectors is considered to improve the beneficiation of Polish sedimentary complex copper ores from the Legnica-Glogow Copper Basin (SW Poland), the upgradeability of which becomes more difficult because of ores grade declining. One group of potential collectors is represented by nonpolar reagents. According to the available literature data, only selected sulfides float in the presence of the nonpolar liquids. The paper presents laboratory scale flotation results for the main sulfide minerals occurring in the Polish copper ores applying either thiol (potassium ethyl xanthate) or nonpolar (aqueous emulsion of n-dodecane) collectors. The investigated feed contained 1.91 % Cu in the form of sulfide minerals such as bornite, chalcopyrite, chalcocite and covellite. Other sulfide minerals including galena, pyrite and sphalerite were also present in the samples. Several flotation tests with various doses of each collector were conducted. Mineralogical analyses of flotation products were carried out and the results compared. A comparison of the results indicated that all sulfide minerals floated well with high recoveries ranging from 91 % to 99 % in the presence of the thiol collector. The use of the nonpolar collector provided results in flotation of sulfide minerals with different terminal recoveries from 61 % for chalcopyrite to 100 % for sphalerite. The most significant differences in flotation in the presence of both types of collector under various conditions of upgrading were observed for chalcocite, chalcopyrite and covellite. Similar flotation results were observed for sphalerite and galena for both collectors. The studies confirmed selective flotation of sulfides from the copper sulfide ores of the Legnica-Glogow Copper Basin in the presence of nonpolar collectors.

Jan 1, 2014

By Anatoly F. Usov, Vyacheslav A. Tsukerman

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

Jan 1, 2003

By Kilian Neubert, Wotruba. Hermann, Lars Weitkämper

Metallurgical slags are produced in large quantities all around the world as a result of smelting, refining or alloying processes applied to metals, ores and recycling material. The slag phase serves different purposes in metallurgical processes. It prevents heat losses and protects the metal phases from contaminations and absorbs gangue and extracted impurities. Due to achievable metallurgical efficiencies certain amounts of valuable metal contents always remain in the residual slag. Recycling of these metallurgical slags has several positive effects, such as optimized ecological and economical compliance of the producing industry. If recycled metal contents can be reintroduced into existing processes, required inputs of raw material can be lowered. High metal prices enable the economic recovery of metal contents in metallurgical slags by applying different non-metallurgical processing methods. Conventional processing of metallurgical slags utilizes processes such as hand picking, selective comminution, screening and magnetic separation. Those state of the art processing techniques have limitations in terms of achievable metal recoveries and required energy demand. The approach for an optimized processing of metallurgical slags targets enhanced metal recoveries in combination with lower specific treatment costs. Processes such as coarse and ultrafine density separation, as well as sensor-based sorting as a pre-concentration stage are used to enable an efficient recovery of metal contents in slags. By applying these methods a completely dry working process is possible. This paper reviews the commonly used methods and describes approaches for innovative processing of metallurgical slags to enhance metal recoveries. Focus of this paper is laid on sensor-based sorting as well as on processes for dry density separation.

Jan 1, 2014

By Graeme Lane, Yuqing Feng, Kaixi Jiang, Junwu Zhou, Zhengchang Shen, Tao Song

"Airlift reactors are used in a wide range of industries, such as hydrometallurgy, biochemical processes, chemical process industry and waste water treatment. With increasing superficial gas velocity three circulation regimes can be defined: no gas bubbles in the downcomer, gas bubbles remain stationary in the downcomer and gas bubbles in the circulating regime. In this paper a numerical modelling method was presented for gas-liquid flow in airlift reactors under different bubble recirculation regimes. Gas-liquid flow was modelled using the Eulerian two-fluid equations, and extra user defined subroutines were incorporated to consider the complex physics, such as bubble induced turbulence and turbulent dispersion force. Some alternative correlations of drag coefficient were used to capture the bubble distributions in the riser and downcomer of the airlift reactor, with consideration of the interaction between bubbles. As using constant bubble size is hard to describe global characteristics of the flow in airlift reactors for three circulation regimes, a model including multiple bubble sizes was presented to get more accurate simulation results of gas holdup and water velocity. Also, the inhomogeneous MUSIG model was used, as an exploration, to compute the complex flow regimes. The MUSIG model is a population balance method to predict the bubble sizes, taking break-up and coalescence into account. The modelling method was applied to a laboratory internal loop airlift reactor, and the simulation results were compared with the experimental measurements of Simcik et al. (2011) for gas holdup and water velocity. The three bubble circulation regimes were observed from simulation figures. Reasonable agreement was obtained over a range of operating conditions, and an improvement was demonstrated using the proposed methods."

Jan 1, 2014

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 Bern Klein, Givemore Sakuhuni

Flotation is the dominant base metal extraction technique and it requires ore to be ground below the liberation size for effective recovery due to its dependence on mineral surface properties. For a poly-metallic ore, differential hardness of constituent minerals leads to over grinding of softer minerals before the harder minerals are fully liberated, which makes selection of a target grind size complex, and the complexity increases when treating leaner ores. Flotation recovery deteriorates above 100 and below 10 microns causing significant loses of valuable minerals in most flotation circuits. Although enhanced gravity concentration is known to be effective at recovering particles above 100 microns, which are difficult to hydro-dynamically transport, exploiting differential specific gravity for base metal separation was not an option in the past. This was partly due to the absence of high mass yield gravity techniques. The advent of continuous gravity concentrators with flexible mass yields, in the past two decades, has necessitated investigation of possible base metal applications. The Knelson CVD, one of the continuous discharge centrifugal concentrators, has an established application niche for sulphides associated with gold. However, its base metal applications have never been rigorously tested. Considering the dependence of flotation recovery on particle size, continuous discharge centrifugal concentration can be integrated in flotation circuits to capture flotation non-recoverable coarse particles. This paper explores how particle size, liberation and mineral hardness influence application of continuous centrifugal technology to regulate galena deportment in a polymetallic base metal plant. The results show that particle size affects galena recovery more than liberation. In view of these results, the CVD can be integrated in the primary grinding circuit to pre-concentrate the heavy sulphides at a coarser grind size with potential grinding energy savings.

Jan 1, 2014

By Majid Saghaeian, Rasool Hejazi, Parisa Ghobadi

"Pulp handling in mineral processing circuits is very complicated due to its inherent different specifications compared with other fluids such as water. Because any variation in ore property (e.g. size and abrasion index) and pulp specification (e.g. density, solid content and pressure) causes problem in this part and reduces the plant availability and throughput as a result. The most common issues in the hose system are sumps and pipe-line blockage, wearing of the pumps impeller and liner, and pipe tearing specially at elbows and bends. High pressure grinding roll (HPGR) is employed in a closed circuit with a screen as the first stage of grinding in Zarand Iranian Steel Complex (ZISCO). Wearing of the pump and pipeline transferring the screen undersize stream was the main problem from the plant commissioning. The plant couldn't achieve to the design capacity because of this defect. Although various practical solutions such as improving the pipes and impeller material quality and eliminating the elbows, as much as possible, were done in order to downtime minimizing, but damages didn’t vanish. Since HPGR discharge contains somewhat rough and abrasive particles, the mentioned modifications didn't effective very much. Therefore, converting of the wet screen to dry and using of belt conveyor to the screen undersize handling was employed based on the plant capability evaluation and experimental and pilot trial results. Although this reformation imposed another additional cost (for conveyor system), but it had significant advantages such as increasing the plant availability up to 96%, reducing the operating costs of the wear parts, providing more stable operating condition for the HPGR performance and decreasing abrasion rate of the HPGR rolls liner because of the lower moist feed."

Jan 1, 2014

By Özcan Y. Gülsoy

Coal beneficiation with optical sorting has not yet been studied in detail. Optical separation of coal from gangue particles as a dry method can be used as an alternative to the other enrichment methods. Developments in optical and pneumatic technology put the optical sorting one step forward by means of applicability of the mechanical sorting to the mineral industry. Because of the inefficient separation performance, dry separation of coal is very limited in industrial applications. Therefore, optical sorting depending on color differences between two minerals can be introduced to coal beneficiation systems. In this study, coal samples obtained from Konya-Ilgin region (Central Anatolia-Turkey) were separated by optical sorter and the results were evaluated. The conventional floatability tests for Ilgin coal are conducted by collecting most of the feed material at 1.3-1.4 g/cm3 density range. Separation of Ilgin coals with heavy medium methods will not be possible because of poor density difference between coal and its impurities. There are important color differences among the floated particles at 1.3-1.4 g/cm3 density range. Therefore, Ilgin coal is subjected to optical sorting in a pilot scale optical sorter. Different size fractions were fed to the optical sorter and then rejected and accepted particles by equipment were analyzed. Ash content of the accepted particles was reduced to 25-35 % and ash in tail increases up to 55-60 % after sorting. Although most of the material floated at low densities, optical sorter separated the feed into two different quality products. This study has the potential to clarify applicability of optical sorting even to non-floatable coals and to provide an important contribution to both industrial applications and literature.

Sep 1, 2012

By Jens Markowski

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

Sep 1, 2012

By P. K. N. Raghavan

Bauxite is the principal source for the production of aluminum metal which has gained tremendous importance over the years due to its versatility as a metal capable of substituting almost all of the non-ferrous metals, non metals like wood, plastics, fibre glass, etc. and even steel in many applications. 90% of the high purity alumina needed for the production of this wonder metal in the world comes from bauxite. Even though alternate methods have been developed to produce alumina from non bauxite sources, owing to the high capital and operating costs involved, Bayer process still retains the superiority among all the methods by virtue of its simplicity and favourable economics. Bauxite continues to be the perfect ore for alumina production and its remarkable utilization makes it the most important non-ferrous ore. Most of the Alumina Refineries in the world process different types of bauxite and that too from varied sources. The technology employed in the Alumina Refineries depends on the Bauxite processed, with an ultimate view to produce alumina of required quality in the most efficient manner. Bureau of Indian Standards (BIS) and Indian Bureau of Mines (IBM) had from time to time put forward bauxite specifications for metallurgical and other applications. However, these are found no fully based on alumina technology, present developments and availability of different types of bauxite in the country. The aim of this paper is to provide scheme of metallurgical grading of Indian Bauxite based on the background of alumina processing technologies and availability of various types of bauxite in the country. Efforts are made here to evaluate beneficiation techniques for central Indian Bauxite from the point of view of alumina production. Keywords: bauxite beneficiation, digestion, alumina, gibbsite, bohemite, diaspore

Sep 1, 2012

By S. Banisi, E. Arghavani, M. Pourkani, M. J. Rajabi, Gh. A. Mohamadian, H. Bidshahri, Gh. A. Parsapour

The Sarcheshmeh copper complex flotation circuit of plant No.1 consists of two identical north and south sections where each includes four rougher (each bank consists of 14 cells), two cleaners (each bank consists of 8 cells), two recleaners (each bank consists of 2 cells), and two scavenger banks (each bank consists of 10 cells). The reduction of feed grade along with a change in the mineralogical composition is the main reason of current lower concentrate grade (24%) compared with the design concentrate grade (32%). Because of a lower feed grade, the amount of rougher concentrate has decreased which in turn has significantly reduced the feed rate to the cleaner, recleaner, and scavenger banks. This has increased the mean residence time of the material in the cleaner section resulting in a lower final concentrate grade. A laboratory study showed that the final concentrate grade can be increased by 2-4% if one cleaner stage is added to the flotation circuit. In this research, based on the laboratory results, one cleaning stage was added to the current flotation circuit. In order to make this modification instrumentally possible in the plant, the final concentrate was gravity transported to the Mo-Cu thickeners. This released 2 pumps and associated tanks which made addition of one cleaning stage practicable. Finally, a part of the cleaner and scavenger cells were used as the third cleaning stage. This decreased the residence time in the cleaner and scavenger banks. After implementation of one cleaning stage in the south section of the plant, the performance of the circuit compared with the identical north section. It was found that at the same recovery, the concentrate grade of the south section increased by 2.5%. The promising results led to the implementation of adding one cleaning stage in all sections of the flotation circuit.

Jan 1, 2018

By A. V. Bogdanovich

Until recently, in consideration of fundamentals of gravity concentration theory, all computations have been based on determination of particles? fall velocity in an unrestricted medium (hydraulic size). Meanwhile, gravity separation processes are realized under conditions of particles? restricted fall, when important and sometimes decisive role is played by interacting forces of particles, dependent on their varying size, density and shape, i.e., segregation forces. We have developed devices and methods for measuring segregation velocities of fine particles of various size, density and shape during their loosening in air or aqueous medium. Besides, to exclude influence of medium upward flows, loosening was provided by superposition of vertical harmonic oscillations on measuring cell. It was established, that maximum segregation velocities are observed at certain optimal acceleration values and amplitudes of oscillations; excessive loosening leads to mixing and worsening of segregation. Velocity of some particles segregation through others depends on particles? size, density and shape, as well as nature of medium (air, water). Absolute segregation velocities of particles in air medium may reach 1~2 mm/s, in aqueous medium such velocities are by an order smaller. Analysis of rare-metal sands material gravity concentration results showed, that owing to segregation process during gravity separation, fine-size isometric particles of heavy minerals are recovered into gravity concentrates more actively, than larger ones, but more elongated in shape. It is convenient and simple to estimate mineral grains? shape by extent of their oblongness, described as ratio of particle minimal dimension to maximum. Besides, mineral mixtures gravity separation results are directly related to extent of oblongness of heavy particles, recovered in gravity separation process, and also to root-mean-square coefficient of their shape variation. The performed research showed that particles segregation in gravity concentration process plays not a lesser role, than hydrodynamics parameters, and demands further theoretical inquiry and experimental studies.

Jan 1, 2014

By Manuel Diaz

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

Jan 1, 2014

By Han Long, He Fayu, Sun Chuanyao

In global mining sector, when people mention "China Factor", usually they refer to China’s huge demands for mineral commodities, which had been driving the world mining industry into late "Super Circle". Few people pay attention to Chinese research capabilities and resources, which actually grows with Chinese economics in last three decades in such a soaring speed that you can simply feel it by the number of papers and attendees in recent IMPCs. In China, currently there are 33 universities and colleges where mineral processing discipline is established, and more than 20 research institutes dedicated in mineral processing area, with the largest number of students, teachers and researchers in the world. Due to the characteristics of Chinese mineral resources, Chinese researchers have made tremendous efforts on R&D of the process and reagents for those low grade, fine dissemination, and complex minerals resources, such as low grade hematite, diaspore, complex poly-metallic sulphides, as well as those minerals rich in China, including scheelite, cassiterite, and rare earth etc. with a special emphasis on the comprehensive utilization. Those research achievements not only successfully commercialized in China, but also have great potential for international cooperation. With continuation of globalization , Chinese government has been encouraging the international R&D cooperation in various areas at all levels, and the funding mechanism is well established with more 400 projects were sponsored in last year,in which,however, the mineral processing related projects are very few. Considering the fact that a large number of Chinese companies or Chinese capitals investing in the mining sector worldwide, more opportunities for international cooperation in this filed wouldbe emerging and increasing, while the factors like complementary, IP, government policy, system and culture difference still need to be addressed properly.

Jan 1, 2014

By Gustav Hawlitschek, Henrique Kahn, Carina Ulsen, Renato Contessotto

"The problems related to waste dumping increased with the growth and development of large cities. In the U.K., more than 50% of landfill waste comes from construction use and the U.S. alone produces around 200 to 300 million tons of CDW annually. The exhaustion of natural sand deposits close to large urban centres stimulates the recycling of construction and demolition waste for the production of recycled aggregates as a construction material. This paper presents a flowchart for the production of recycled sand with low porosity and regular shape by the selective removal of the cement paste attached to recycled aggregates. The products characterization was carried out by the determination of the particle size and shape distribution, chemical and mineralogical composition, heavy liquid mineral separation and quantification of all present phases using a scanning electron microscopy with automated image analysis (SEM-MLA). The comminution of CDW by vertical shaft impact crusher made possible the production of a lower porosity recycled sand. The heavy liquid mineral separation showed that the proportion of low porous phases (d>2.5 g/cm3) is very high, exceeding 70% of the weight, encouraging further mineral processing separation to obtain a fine recycled aggregate with less cement paste content. The mineralogical characterization by XRD and SEM indicates that the main phases are tectosilicates, phyllosilicates and calcite which one can be attributed to both calcareous aggregate and cement paste. The precise quantification of cement paste and calcite/dolomite alone is just possible by automated image analysis. The characterization results demonstrated that proportion of phases with no cement paste attached increases progressively in denser products. The results of heavy liquid separations and image analysis are comparable and automated image analysis can be used for the characterization of phase content and their main associations."

Jan 1, 2014

By Slobodan B. Vujic

"Some twenty years ago, during construction of flotation in the “Veliki Krivelj” copper and non-metallic mine Bor, a computer supported system for remote controle of technological process was installed. Nowadays, the major part of equipment of this system is worn-out and technically old-fashioned. Having this in mind a decision was made to design a new computer supported information-management system for Flotation. The paper presents a concept and features of project solutions.For the requirements of remote monitoring and management of technological process in Flotation of “Veliki Krivelj”, Copper and non-metallic minerals mine in Bor, Yugoslavia (hereinafter: CNM Bor), a measuring-regulation equipment was implemented and a computer control system, adjusted for that time, built some twenty years ago. The major part of this equipment is today worn out and technically out of date.Having estimated that production and business activities could hardly be more efficient, operative and successful on one hand, and available mineral and other resources rationally exploited, the CNM Bor made a decision in 1999 to improve information-management function of Flotation. The idea was that the set task be realized through development and introduction into practice up-to-date integrated and computer-supported production-business information-management system. The first logic step in completion of this task refers to engineering-creative determination of information management system (hereinafter: IMS), namely to project elaboration.When considering the real system from technical, technological, organization, monitoring-management, logistic and business aspects, the Project on IMS of Flotation, should provide a rational, modern and, for the real system conditions, complete solution. The Project solutions should be based on the most recent knowledge from computer and measuring-regulation technics as well as from CIM concept (Computer Integrated Manufacturing)."

Jan 1, 2003

By Dingwu Feng, Jannie S. J. van Deventer

"The effect of ultrasonication on reactions at solid/liquid interfaces was investigated by using an ultrasonic probe in two slurry systems, i.e. cyanidation of a refractory sulphide ore and geopolymerisation of metakaolinite. The surfactant dithiophosphate was used to render the gold bearing sulphide particles hydrophobic, in an attempt to induce the formation of cavitation bubbles directly at the desired surfaces. Oxygen was injected into the cyanidation system to improve the attachment of oxygen bubbles to the hydrophobic sulphide surfaces. Geopolymerisation occurs in highly alkaline solution with waste aluminosilicate oxides and silicates as the reactants. The process of geopolymerisation is believed to involve dissolution of Al-Si oxides from solid particles, diffusion of dissolved Al-Si complex from the solid surface into the gel phase, condensation of gel phase and hardening of the gel phase. It has never been investigated how ultrasonication affects the above steps in synthesising geopolymers, despite a number of papers dealing with sonochemical synthesis of materials. The introduction of power ultrasound into such slurry systems is expected to result in advanced geopolymer materials.In the cyanidation of the pyrite concentrate, the kinetics of gold extraction were significantly enhanced in the presence of ultrasound, due to the prevention of passivation and the enhanced dissolution of sulphides. Cyanide consumption was significantly reduced with ultrasonication, owing to the oxidation of soluble sulphides to sulphate, minimising the cyanide consumption by sulphides. With oxygen injection, ultrasound significantly enhanced the leaching of gold from the pyrite concentrate, as oxygen could enhance the formation of the oxidation radicals by ultrasonic cavitation. In the presence of dithiophosphate, ultrasound further improved gold leaching in the oxygen-aerated system. Dithiophosphate could selectively adsorb at gold host sulphide surfaces, and make the surfaces hydrophobic. As a result, the ultrasonication effectiveness could be enhanced through forming cavitation bubbles directly at the interfaces."

Jan 1, 2003