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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 Francis Pitard

"The optimization of metallurgical processes requires an in-depth understanding of the heterogeneity carried by any constituent of interest. It emphasizes that knowledge of the Theory of Sampling (TOS) is the necessary step to ensure that valuable and valid research programs, pilot plants, feasibility studies, plant design and plant operations have been set on solid foundations. Too many publications today are solely based on the properties of the sample, with no mention of how this sample relates to anything in the environment where it was collected. Unfortunately sampling is an error-generating process that leaves no apparent tracks of its shortcomings. Indeed, it is easier to track down analytical errors than sampling errors. Consequently, bad sampling practices plague the scientific community and the industry and are responsible for severe money losses, unsatisfactory science and processing, and sometimes litigation. A point-by-point strategy is presented addressing sampling problems in early stages of a project. Sampling system requirements for metallurgical accounting and process control are listed. The use of Chronostatistics is suggested to determine if sampling systems are performing satisfactorily and to identify the various types of process variability that may not be easily detected by a conventional inspection of available chronological data. This strategy will help engineering firms, manufacturers, managers and supervisors to provide, install, use and maintain key sampling systems located at very important points in a process. Equipped with the appropriate sampling and statistical tools it becomes easier to minimize reconciliation problems with the mine, with suppliers and with clients. Contrary to the beliefs of many people, good sampling systems are not expensive because in the long run they help to reduce hidden cost and better regulate plant productivity; they most certainly minimize the number of unnecessary meetings looking for solutions where there are none. The suggested strategy will help specialists to extract maximum information from the available data, as large investments and crucial decisions depend on it."

Jan 1, 2014

By Valery V. Kostjuk, Victor. N. Bredikhin, Alexander I. Shevelev, Evgeny A. Kazban

"The investigations to improve the process data have been done in order to stabilize the functioning of drying units. The scheme of turnings preparation with centrifuging and subsequent thermal degreasing (tandem) is proposed. To improve the efficiency of the process the scheme of reclamation of the centrifuge fugate is developed with production of oil and service circulating water. Empirical dependences of the turnings temperature influence on the lubricant-coolants content in centrifuging are gained. When the turnings temperature is increased to 80 C the residual content of LC is decreased by 1.5%. The investigations aimed to improve the preparation of non-ferrous turnings have allowed to decrease the melting loss by 15-20%; to stabilize the process of thermal drying of turnings; to decrease sharply (by 60- 70%) the volume of LC combustion products; to reclaim the centrifuge fugate and produce oil and servicecirculating water.Non-ferrous turning and primarily aluminum and copper alloys turning is a stable source of secondary raw materials for metallurgical works.Direct by lubricant-coolants (LC) of various types: synthetic, semi synthetic, oily and emulsions.On the base of investigations concerning various methods of the non-ferrous turning processing the favorable one has been selected taking in to consideration the economy, ecology and quality of the finished product (alloy). Two-stage process is developed. The main idea of the process is the elimination of the lubricant-coolants (LC) to the limit specified in advance. The applied method is centrifuging with subsequent final elimination of LC by thermal method.Constant value of LC content at the inlet of the thermal unit excludes practically the oxidation of metal and as a consequence increases the output by 10 –15 % in metallurgical processing."

Jan 1, 2003

By Hermann Wotruba, Lars Weitkämper

"Dry coal dressing was popular during the 1950.s and 60.s in many parts of the world. The devices mainly used were air jigs and air tables.The increase in ash and moisture content of run-of-mine coals due to the wide advanced mechanisation of mining mechanisation during and after this period led to that pneumatic devices being unable to treat run-of-mine coals with the desired efficiency. Since the 1960.s almost all new coal preparation plants have been based on wet processes that are highly efficient in terms of coal recovery and their ability to handle damp and sticky run-of-mine coals. (Frankland, 1995)However, water is becoming increasingly costly and the disposal of fine products, containing most of the water, is an environmental concern. There would be significant cost savings and a lower total energy consumption if coal could be cleaned dry. Efficient dry coal treatment would be an interesting solution in desert, arid or cold areas.In Germany one dry coal dressing plant is in operation. The process and the advantages and disadvantages are presented below.Further on new developments in the field of dry density separation of coal are reviewed and analysed. Test results of new dry coal separation methods e.g. new developed air jig and magnetic separator are reported."

Jan 1, 2003

By M. Schneider, J. Regler, Th. Neesse, AKW A. + V GmbH & Co., J. Dueck, F. Donhauser

"In practice the advantages of high-quality hydrocyclone separation are often reduced due to varying feed suspension properties, solids concentrations and particle size distributions. Therefore, a new control system for a battery of hydrocyclones with a nominal diameter of 150 mm was developed for bentonite slurry regeneration associated with tunnel excavation using bentonite slurry as a transport aid and lubricant.As can be seen from Fig. 1, the hydrocyclone battery has been modified for regulation purpose. The battery was manufactured with an overflow collector as a closed pressure chamber (1) with a discharge pipe (2) where the throttling valve (3) was installed.With increased stepwise throttling of the overflow, the volume split is changed with the effect that the solids discharge in the underflow is increased. To stabilize the total throughput, the feed pump speed is simultaneously increased so that the pressure drop ?p across the hydrocyclones (9) remains approximately constant. However, this causes the increasing pressure inside the hydrocyclones, which results in a further intensification of the underflow discharge. After the detection of the break through of the air core (transition state) by the capacitive sensor (4), the throttle valve is shortly opened, and a new regulation interval can start again. The control concept is focused on maintaining the optimum operating state, characterized by the underflow discharge shape at the transition state between rope and umbrella discharge."

Jan 1, 2003

By W. G. Wu

More and more researches and applications of organic chelating agents as depressors or activators are carried out in the course of research and application of modern flotation. The paper puts forward the necessary condition of organic chelating agents as depressors or activators by analyzing the chelating chemical performance of organic chelating agents with metal ions and the stability of chelates formed by them; at the same time, puts forward four sufficient conditions of organic chelating agents as depressors or activators according to different hydrophilic capability of the chelates and different performance of depression and activation of organic chelating agents for minerals. Namely, the ?1+1/4? necessary and sufficient conditions of organic chelating agents as depressors or activators are put forward.

Jan 1, 2014

By Gökçe Törenli, Okay Tutar

"Predicting the performance of plant-scale comminution circuits is essential to monitor the energy use and product size distribution, allowing us to control and optimize the whole process. In the light of this issue, with the assist of recent technologies, simulation techniques utilize the chance of putting the theory into practice in the most accurate way. For this purpose, this study aims to evaluate and optimize the efficiency of a plant-scale ball mill circuit by using perfect-mixing ball mill model on a simulation environment. The comminution circuit is selected from a specific copper-ore processing plant in Turkey. The essential parameters which are required for this study such as fresh feed Bond work index, size distribution etc. are determined by laboratory experiments. The forecasted data which are calculated by third-party software will be compared by the industrial operating data, in order to determine the performance of comminution circuit. In addition to that, this methodology provides a greater ability to analyse, optimize and understand the comminution circuit of ore treatment plant. The authors believe this work will provide supplementary data for further studies on simulation and subsequent optimization of comminution circuits.INTRODUCTION By the assist of mathematical models of the grinding mills and classifiers, simulation of the grinding circuits become more common in comminution because it is relatively economical and able to consider many variables simultaneously. It’s proceeds depends on the accuracy of the models and capability of reflect real operations. Computer-based simulation studies would provide the quantified information about the effects of the proposed changes on the comminution circuit performance in terms of size distribution, mass flow rates, equipment efficiency etc. Then the mentioned data used in order to check the suitability of the current equipment to the modified conditions, and for equipment selection. The outputs of circuit could also be used to estimate downstream flotation circuit performance because the general aim in this study is to The aim of the study is to investigate optimum operating variables and achieve p(80) size of 57 µm and 64 % of -36 µm particle in hydrocyclone overflow stream, which is optimum for that porphyritic copper ore for best concentrate recovery after flotation process in specific copper ore comminution circuit by using modelling and simulation techniques. Sampling survey was carried on the fine ore bin in order to perform Bond work index test and determine work index value (Wi). Thereafter mass balancing, using the size distribution data and tonnages, models for ball mills and hydrocyclone were developed. Finally, the circuit performance were investigated by computer simulations via JKSimMet software."

Jan 1, 2018

By D. Saramak

"High-pressure grinding technology is considered as one of the most efficient techniques of ore comminution, especially in terms of energy consumption. HPGR devices has been utilized in many mining-related industrial sectors, including iron and non-ferrous metal ores processing (copper, platinum, gold), as well as cement and limestone flour production. Even though the technology well known (introduced into mineral processing circuits in 80’s), there are still examples of ineffective operation of HPGR devices. This is a result of improper application of HPGR into individual crushing circuit. The purpose of the paper was to analyze selected effects achieved in HPGR on the course and effectiveness of beneficiation operations. Investigations were carried out for copper ore, and investigative programme was run for different values of HPGR pressing force, as well as changeable ore characteristics (content of fine size fractions, material moisture). All crushing products were then treated in flotation process, in order to determine useful mineral recovery. Results of investigations show that HPGR operating pressure influences the metal recovery in proportional way, however too extensive pressure values have relatively lower impact on increasing of the metal recovery. Particle size distribution of HPGR feed and its moisture have lower influence on recovery level than HPGR pressure, but too extensive moisture content influences the higher energy consumption of the roller press, together with less effective comminution. The second aspect raised in the paper was a possibility to control and optimize the HPGR-based circuit. There were presented the proposed approach to adjustment of HPGR operating parameters that enables the higher metal recovery.INTRODUCTION The high-pressure grinding technology, invented and developed by Professor Schoenert in 70’s (Schoenert, 1979), is currently regarded as one of the most efficient methods of hard ore comminution. Since then the technology was introduced into raw materials treatment circuits in many mining and mining-related industrial sectors, including iron and non-ferrous metal ores processing (copper, platinum, gold), as well as cement and limestone flour production. Considerable number of works concerning modeling and optimization of HPGR operation were also presented (Daniel & Morell, 2004, Tavares, 2005, Saramak, 2012, Saramak & Kleiv, 2013). Nowadays high-pressure grinding rolls devices are considered as well know technology with over 500 sold machines, according to various sources."

Jan 1, 2018

By M. E. Ramírez

In this research bioleaching or extraction of iron present in a kaolin from La Virgen mine, Anti-oquia/Colombia, was carried out. Organic acids produced in SF with Aspergillus niger were used in the process. The fermentation process was carried out in 3 L aerobic stirred bioreactors, at a temperature of 30 °C, a stirrerd speed of 700 rpm, an initial pH of 4 and a fermentation time variable between one to 8 days, obtaining broth fermentation samples daily per bioreactor. For iron extraction, fermented broth from second to sixth day of fermentation was evaluated and it was found that the fermentation broth of the third day showed a larger potential for iron removal, 786 ppm, by using kaolin with an initial iron content of 1401 ppm. A set of tests using commercial organics acids such as citric acid and oxalic were carried out because those were found in the fermentation broth and it was found that oxalic acid presented three times more iron removal than citric acid.

Jan 1, 2014

By J. K. Wen

The Mojiang nickel deposit is situated in Mojiang county, yunnan province, a tropical area in the southwestern China. The known geological resource (measured and inferred) includes 4 million tons of nickel sulphide ore at an average grade of 0.50% Ni and 0.34% As. Nickel minerals are mainly gersdorffite (NiAsS), millerite(NiS), morenosite (NiSO4?7H2O), and more than 50% nickel minerals is gersdorffite which contains arsenic. Pyrite is the dominant sulfide mineral, 22% in the ore and part of nickel minerals are locked in pyrite. It is difficult to attain the nickel concentrate quality allowed by a smelter and the acceptable nickel recovery through flotation due to the high arsenic in the ore and the nickel minerals locked in pyrite. The shake flask tests and column tests for nickel recovery from the Mojiang nickel sulfide ore had been finished by the end of 2003. The column bioleaching tests were carried out using the columns with diameter of 120 mm and height of 1200 mm, and 70% of nickel dissolution was attained in 300 days. A 10,000t pilot test heap was built in the Mojiang Nickel Mine by June 2003. The ore used in the test heap was supplied from the underground mine and was crushed to -20 mm before being feeding to the test heap, which is 4~5 m high, 30 m wide and 50 m long. The naturally adapted mesophile and moderate thermophile have been inoculated into the leaching pile by June 2003. The operating temperature in the heap ranges from 38? to 55?, varying with season. 30% of nickel dissolution was achieved in 3 months and the typical pregnant leach so-lution (PLS) contains 2~3 g/L Ni and 20~30 g/L Fe. The Ni sulfide which was produced by us-ing Na2S 10 t/t?Ni contains 16%~20% Ni and Ni recovery was 98%. 70% of Ni dissolution is expected in 12 months. The test heap was scaled up to 60,000 t of ore per year by mid of 2005. In this paper metallurgical studies and performance of the pilot test heap will be described. The results of mineralogy, shake flask tests and column tests on bioleaching of the nickel sulfide ore are reviewed. The key test heap operation parameters, the performance of bio-heap leahing-Na2S precipitation, ferrous oxidation-ferric precipitation-Na2CO3 precipitation, bacteria in the pile, water and acid balance, effluent disposal, capital and operation costs are also discussed.

Jan 1, 2014

By J. Seo, W. Kim, I. Bae

"Microcrystalline silica impurities such as quartz and opal-CT commonly associated in bentonite should be controlled and removed as far as possible when bentonite is used as biocompatible raw material because they show sufficient evidence of carcinogenicity. Since opal-CT contained in bentonite in trace amounts cannot be well separated by conventional sedimentation method, in this work, the ultrasound-assisted removal of the impurity was attempted. Irradiating ultrasound into bentonite-water suspension promoted the production of fine montmorillonite particles in the suspension and the production markedly increased when montmorillonite was activated by Na2CO3. Subsequent centrifugation of the suspension made it possible to recover pure montmorillonite particles as an overflow product. Only 16.2 mass % of total solids was recovered as an overflow from the non-activated suspension, whereas 63.5 mass % was recovered from the activated suspension at centrifuging speed of 10000 rpm. Increasing sonicating time enhanced the yield of overflow, however, excessive sonication up to 10 min hindered the purification of montmorillonite. It was observed that the peak reflection of (101) plane of opal-CT in overflow increased as sonicating time increased during prolonged sonication. INTRODUCTION Bentonite consisting predominantly of mineral montmorillonite is clay-rich soft rock generated frequently from the alteration of volcanic ash. Depending on the nature of its genesis, bentonite contains a variety of accessory minerals, which may include mainly quartz, feldspar, opal cristobalite/tridymite (opal-CT), calcite, illite and mica. The presence of these accessory minerals can impact the industrial value of the deposit, reducing its commercial value depending on its applications. Therefore, bentonite is often purified by removing these impurity minerals for special applications where specific properties and characteristics are required (Murray, 1999). Among the special applications, bentonite is often used in the cosmetic and pharmaceutical industry as both excipient and active ingredient in the forms of liquid (suspensions, emulsions), semi-solid (creams, ointments) and solid (powder, capsules and tablets). The basic requirements for bentonite to be used as raw material are pure, microbiological and mineralogical inertness. Physical properties such as swelling volume and gel formation are also important. Particularly, microcrystalline silica polymorphs such as quartz, cristobalite and opal-CT should be controlled and removed as far as possible because they show sufficient evidence of carcinogenicity in humans."

Jan 1, 2018

By Lev Malytin, Alexander Dyachenko, Roman Kraydenko

"A new method of processing beryllium raw materials based on interaction of beryllium mineral with ammonium fluoride was developed. Possibility of extracting ammonium tetrafluoroberyllate from bertrandite and phenakite minerals is proved. The developed technology allows replacing the outdated sulfate technology developed by Materion Corporation. INTRODUCTION Beryllium is a strategic metal, which is produced only in three countries: the USA, China and Kazakhstan. The world production of beryllium amounts to only 300 tons per year. More than 75% of the world beryllium production is manufactured from oxide beryllium ores in the USA by Materion Corporation. In Russia there is a large-scale beryllium ore deposit «Ermakovskoye» containig over 1 million ton of ore. Concentration of beryllium in ore amounts to 1,2%. Since the mineral base of ore is calcium fluoride, the sulfate technology of Materion Corporation cannot be used. After alloying and sulphuric acid leaching the fluorine-ion found in fluorite and beryllium together evolve into the aqueous phase. At the stage of Be(OH) precipitation fluoride-ion prevents complete isolation of beryllium into the phase of hydroxide, which increases the loss of beryllium. A new ammonium-fluoride method for processing high-fluoride beryllium ores has been developed at Tomsk Polytechnic University. The ammonium-fluoride method involves fusion of ammonium fluoride (NH4HF2) with a beryllium concentrate. The concentrate containing 10% of beryllium oxide and 25% of calcium fluoride is produced by flotation from the ore of Ermakovskoe deposit. The main component of the ore concentrate is fluorite CaF2, which does not react with NH4HF2. Beryllium in this concentrate is represented by two minerals: phenakite Be2(SiO4)2 and bertrandite Be4[Si2O7](OH)2. Ammonium fluoride, unlike sulfuric acid, does not react with calcium fluoride and is not consumed for decomposing the mineral base of the concentrate. Ammonium fluoride is an accessible and environmentally safe reagent, worth up to $ 1,200 per ton. The total amount of ammonium fluoride is recycled and is used for decomposing a new batch of beryllium concentrate."

Jan 1, 2018

By Lev Malytin, Alexander Dyachenko, Roman Kraydenko

"A new method of processing beryllium raw materials based on interaction of beryllium mineral with ammonium fluoride was developed. Possibility of extracting ammonium tetrafluoroberyllate from bertrandite and phenakite minerals is proved. The developed technology allows replacing the outdated sulfate technology developed by Materion Corporation. INTRODUCTION Beryllium is a strategic metal, which is produced only in three countries: the USA, China and Kazakhstan. The world production of beryllium amounts to only 300 tons per year. More than 75% of the world beryllium production is manufactured from oxide beryllium ores in the USA by Materion Corporation. In Russia there is a large-scale beryllium ore deposit «Ermakovskoye» containig over 1 million ton of ore. Concentration of beryllium in ore amounts to 1,2%. Since the mineral base of ore is calcium fluoride, the sulfate technology of Materion Corporation cannot be used. After alloying and sulphuric acid leaching the fluorine-ion found in fluorite and beryllium together evolve into the aqueous phase. At the stage of Be(OH) precipitation fluoride-ion prevents complete isolation of beryllium into the phase of hydroxide, which increases the loss of beryllium. A new ammonium-fluoride method for processing high-fluoride beryllium ores has been developed at Tomsk Polytechnic University. The ammonium-fluoride method involves fusion of ammonium fluoride (NH4HF2) with a beryllium concentrate. The concentrate containing 10% of beryllium oxide and 25% of calcium fluoride is produced by flotation from the ore of Ermakovskoe deposit. The main component of the ore concentrate is fluorite CaF2, which does not react with NH4HF2. Beryllium in this concentrate is represented by two minerals: phenakite Be2(SiO4)2 and bertrandite Be4[Si2O7](OH)2. Ammonium fluoride, unlike sulfuric acid, does not react with calcium fluoride and is not consumed for decomposing the mineral base of the concentrate. Ammonium fluoride is an accessible and environmentally safe reagent, worth up to $ 1,200 per ton. The total amount of ammonium fluoride is recycled and is used for decomposing a new batch of beryllium concentrate."

Jan 1, 2018

By Boris Albijanic, Hongjuan Chen, Bogale Tadesse

"During mechanical flotation of fine liberation sized complex rare earth ores, a large fraction of ultrafine valuable mineral particles are lost to tailings. Fine gangue mineral particles can be entrapped within the froth phase and be floated together with target mineral particles. Another common challenge in ultrafine rare earth mineral flotation is the formation of a sticky froth (excessively stable froth). Thus, the improvement of the flotation of fine and ultrafine rare earth bearing minerals through appropriate cell design and reagent selection is highly desirable. The aim of this study is to investigate the performance of a pico-bubble cavitation flotation column in improving selective recovery of ultrafine rare-earth elements (REEs) bearing minerals from complex and low-grade ores. In pico-bubble cavitation column, very small bubbles are generated which are capable of attaching to ultrafine particles and consequently modifying their surface properties. The overall effect of these processes should lead to improved flotation selectivity and recovery of ultrafine RE mineral particles. In this paper, the effects of a number of flotation operating variables on recovery and grade of REE minerals was investigated using a continuous pilot scale pico-bubble column flotation. At the flotation conditions used in this study, subtle monazite upgrade was observed while gangue Fe oxide was preferentially floated even in the presence of depressants. INTRODUCTION Rare earth elements (REEs) have unique properties such as superconductivity and catalytic activity, and are in high demand for a large number of cutting-edge technologies in the modern world including the production of mobile phones, fuel cells, displays, permanent magnets for wind power generation, high-capacity batteries, green energy devices, etc (Naumov, 2008). REEs tend to be intimately associated within many minerals, and are rarely found in high concentrations in deposits for economic extraction. Up to now, among over 250 minerals containing REEs, bastnasite (Ce), monazite (Ce, Th and La) and xenotime (Y) are the three main minerals that contain sufficient grade of REEs for commercial exploitation (Zhang and Edwards, 2012). The deposits that contain bastnäsite, monazite and xenotime usually have complicated mineral compositions, with various valuable minerals of fine embedded grain sizes in association with complex gangue minerals. In order to ensure liberation of the REEs minerals, fine grinding to less than 30 µm is necessary. This fine grinding leads to difficulty in recovering a large proportion of fine and ultrafine particles in separation processes such as flotation (Trahar and Warren, 1976). Consequently, highly liberated and ultrafine fine valuable REEs particles are lost into tailings during traditional mechanical flotation. Besides, the formation of extremely sticky and stable froth inhibits the drainage of hydrophobic particles. Thus, improving flotation of rare earth bearing minerals, particularly the ultrafine size range, is highly desirable."

Jan 1, 2018

By S. J. Ma

To look into the ionic release laws of the sulphide tailings in some copper mine, the effects of the soaking period, temperature, oscillating speed, and pH of the solution on the heavy metals ionic re-lease were investigated through static soaking leaching experiments. The results show that Cu2+, Zn2+, Pb2+, Cr3+ are of different leaching behaviors with soaking period. The ionic concentration in soaking solution for four ions has a great gap. Zn2+ is more easily released out of sulfide tailings than Cu2+, Pb2+, Cr3+ , and the ion release concentrations are not proportion to their contents in the tailings. The time for each ion to reach its maximum concentration are different. The minimum concentration do not occur at the first day. Each ion concentration shows different fluctuation characteristic during soaking process. Solution pH, oscillating speed, and temperature affect the releases of Cu2+, Zn2+, Pb2+, Cr3+ out of the tailings to different extent. The effect of pH value on ion re-lease for the four ions ranks as Zn2+>Cu2+>Pb2+>Cr3+, the oscillating speed ranks as Pb2+>Zn2+>Cu2+>Cr3+, and the temperature ranks as Cr3+>Pb2+>Zn2+>Cu2+.

Jan 1, 2014

By G. Unland

The sizing of crushers depends on the expected crushing forces. However, the crushing forces develop differently with every individual rock while it is compressed by the working surfaces of the crusher. For sizing, this compression process has to be characterized by the maximum crushing force. The maximum crushing force depends on the strength, shape and size of the rock, the amount and velocity of the imposed displacement of the working surfaces of the crusher on the rock and the conditions of the contact surfaces. From experience it is known that the strength of the material and, therefore, the crushing forces depend on the size of the specimen. This dependence is the so called size effect. The determination is based on compression tests. The force development is recorded during the compression of the specimen and for every individual test the maximum force is determined. The occurring maximum crushing forces of several rocks with the same diameter comminuted under the same conditions can be assessed by a mean value and a variance. The relationship between the mean values of the cross section related maximum crushing forces FAmax and the corresponding sizes d of the specimens can then be described by mathematical functions. They are derived from different approaches (phenomenological, statistical and statistical-physical methods). The phenomenological methods are subjective and yield functions depending on the assumptions of a person, whereas the statistical and statistical-physical methods are based on an evaluated function and the optimization of the parameters.

Jan 1, 2014

By Graeme J. Jameson

In conventional flotation machines, the recovery is strongly related to particle size. As particle size increases, the recovery also increases, reaching a maximum in the range 20 to 120µm. Beyond this range however, the recovery declines quite quickly. The reason for the decline in recovery observed with coarse particles can be traced to the effect of turbulence. Bubbles trapped in turbulent eddies rotate rapidly, and when the centrifugal force on a particle exceeds the retaining forces due to surface tension, the particle detaches. Since the centrifugal force varies as the cube of the diameter of the particle, and the attachment force varies simply as the diameter, being proportional to the length of the contact line, it is clear that detachment forces will predominate as the particle size increases. The corollary is that the recovery of coarse particles can be improved if the level of the turbulence in the cell can be reduced to a minimum. In this paper, a new type of flotation machine will be described, in which the particles to be floated are suspended in a fluidized bed. An up flow of fluidizing water is provided, by recycling liquid from the top of the cell. The recycle stream is aerated in a high-energy device that disperses the air into fine bubbles that capture the fines and ultrafines. Results are presented for several minerals and coarse coal. Keyword: fluidized bed flotation

Sep 1, 2012

By P. Radziszewski

In comminution research, ore breakage and wear are usually studied independently of one another. Much of this is due to the fact that wear is usually a slow process compared to ore kage. However, the abrasion wheel test used to determine the abrasive wear contribution to total steel media wear provides the opportunity to study not only abrasive wear and friction but also ore breakage. In this paper, we will explore the use of the abrasion wheel wear test device to study abrasive wear, friction and ore breakage using standard Ottawa foundry sand. We will look into the feasibility of applying the work index as well as t10methodologies to this test set-up. We will also look at how the work index results evolve with abrasive wear and friction. We will then discuss the merits of pursuing the use of this abrasion wheel test for not only wear characterization but also breakage characterization.

Jan 1, 2014

By Regis Texeira, Leopoldo Gutierrez, Vicente Hernandez, Caludia Vidal, Lina Uribe

"Molybdenum is currently the most important by-product of Chile´s copper mining industry. This mineral has gained international relevance over the years, because of its price. At mining deposits in Chile, copper and molybdenum are extracted together and then separated in a concentration process consisting of several flotation steps using sodium hydrosulfide (NaHS) as copper depressant. However, there are environmental issues related to the potential emisions of toxic hydrosulfide gas and bad odours, which affects nearby communities and suppose a risk for operators. This problem has led to the need for development of new technologies to eliminate the use of NaHS in the process of selective flotation of Cu and Mo minerals. In this work, results of flotation tests in which lignin derivatives reagents are used to obtain the selective separation of Cu and Mo minerals by flotation are presented. In this technology molybdenite is depressed by the action of lignin derivatives (lignosulfonates), while copper sulfides remain hydrophobic and float. The use of lignin derivatives in the selective flotation of copper molybdenum minerals represents a non-toxic alternative to NaHS.INTRODUCTIONSeparation of copper sulfides from molybdenite is commonly achieved through a two-stage flotation process. In the first stage the collective flotation of copper sulfides and molybdenite is promoted to generate a collective concentrate which is then treated in a second stage with sodium hydrosulfide (2.5-3.0 kg/t NaSH) to depress copper sulfides flotation without affecting the flotation of molybdenite. As a result a copper concentrate with 30-35% Cu, and a molybdenum concentrate with 50-52% Mo are generated. Although this process is widely used at industrial level, environmental issues related to the risk of H2S generation and bad odors have always been a concern. Thus there is a need in the industry for a more environmentally friendly process to separate copper sulfides and molybdenite."

Jan 1, 2018

By V. Panayotov

Slag and by-products of metallurgy bear valuable components and their processing raises an in-creasing interest. Coke and iron have to be separated and other components have to be depressed, in order to obtain sellable high quality copper concentrates. Use of classical mineral processing technologies, such as magnetic separation, sulphidization, hydrometallurgy, etc. yields copper concentrates with grade of 4%~6% Cu. Copper is lost in tailings and the whole technological cycle is low profitable. Technology proposed applies an electrochemical treatment of the industrial water entering the flotation cycle. Iron and iron compounds that do not bear Cu, coke and gangue materials are depressed during the copper flotation. Copper concentrate of grade of 9.8%~10% Cu is obtained at simultaneous increase of Ag recovery by 8%~10%. As a result company profitableness is increased. Technology proposed is easy to implement, it does not require changes in the existing technology flow-sheet, and additional investment is low. The flotation process can be aided by a specially developed system for real-time analysis of the obtained copper concentrate which allows in-time corrections in the flotation parameters and entire process control. Applied flotation schemes, technological parameters and results obtained are described.

Jan 1, 2014