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By A. Qaredaqi, M. Mohammadi

Wet High Intensity Magnetic Separators, for short, WHIMS are used for recovery of Iron ores with low magnetic susceptibility. A Jones patent WHIMS with "grooved plates" matrix is being used in Dry Tailing processing line in Hematite Recovery Plant at Golgohar mining & Industrial Co. for recovery of Hematite. In this kind of separators Matrices are used for increasing the Magnetic field intensity and providing high magnetic field gradient. The laboratory WHIMS in Golgohar Iron Ore and Steel research Institute is capable to provide a background magnetic field strength up to 0.85 Tesla and in presence of ‚expanded metal? matrix, magnetic field intensity could increase up to 0.9 Tesla. More than 50% of feed particles in this separator were finer than 36 micron and recovery of these particles needs more magnetic field intensity. Hence, ‚Grooved Plates? matrices with Js= 2 Tesla and 3.8 mm gap were constructed. Measurements indicated that magnetic field intensity around the matrix will increase to 1.25 Tesla. Graph of Magnetic field intensity around the matrix to background magnetic field intensity was plotted and a model with Rsquare= 0.9 was offered. In addition, magnetic field gradient and magnetic force were calculated. In WHIMS with feed top size of 150 micron, the main effective forces on separation process are the magnetic force and the hydrodynamic drag force. With assuming that the particles are smooth and spherical and the flow is laminar, Recovery of fine magnetic particles is problematic in this separator because of drag force. Considering these facts and mentioned model, finest particles that are recoverable in different magnetic field intensities were calculated. Computations illustrated that with magnetic field intensity more than 0.8 Tesla, particles as fine as 4 micron are theoretically separable but it should be noted that in practice a larger attractable particle size would be expected.

Jan 1, 2014

By T. N. Aleksandrova, A. V. Afanasova

"The research is aimed at solving the problem of enrichment of sulphide ores, counting for more than 40% of the reserves in Russia. The aim of the research is to develop and scientifically substantiate the scheme for processing this type of ores in order to extract fine-dispersed noble metal particles (FNMP). In this work samples of sulfide carbonaceous ore and flotation concentrates were analyzed using complex precision methods of analysis: electron microscopy, spectral analysis with induction plasma, complex thermogravimetric analyzes, etc. Data on the composition of the organic constituent of the samples were obtained with the usage of complex thermogravimetric analysis. The presence of various types of kerogen and bitumen has been established. Experimental studies on the coarsening of FNMP from the initial ore and flotation concentrates using electromagnetic radiation have shown the effectiveness of this coalescence method. The data on the elemental composition of the samples and the amount of FNMP were obtained. Thus, studies on the extraction of FNMP from carbon sulphide ore have shown the possibility of effective usage of combination of electromagnetic action and classical enrichment methods to extract fine particles of noble metals. INTRODUCTION Due to the depletion of free-milling raw materials the involvement of new types of deposits is the strategy of developing mining industry of Russia. The black shale raw materials show interest as a non-traditional source of precious metals since its genetic and positional gold-carbon connection. Muruntau, Sukhoi Log, Bakyrchik, Natalkinsky, Nezhdaninskoye, Olimpiadinsky, Homsen and others are the examples of well-known deposits of the black shale formation [1]. In fact the main gold-dispersed regions of Russia are composed of black-shale strata. Review of literature [2-5] shows that in recent years in almost all deposits of the black shale formation metals of the platinum group (PGM) were detected that significantly increases their practical importance."

Jan 1, 2018

By József Faitli, Imre Gombköto, Barnabás Csoke, Tamás Magyar, Beáta Oláh, Sándor Nagy

"Raw materials are among the main building blocks of a growing economy. Without raw materials, no matter whether it is primary or secondary, production is not possible. Products with high added value require special materials. Recently, worldwide production of some important raw materials mainly comes from a handful of countries, for example: China (Rare Earths Elements (REE)), Russia, South Africa (Platinum Group Elements (PGE)), Democratic Republic of Congo (Cobalt), etc. In the EU as well as in Hungary, the importance of the so called 14 critical raw materials has been recognized. Within the frame of the TÁMOP-4.2.2.A-11/1/KONV-2012-0005 - CriticEL project, the Institute of Raw Materials Preparation and Environmental Processing in cooperation with the Institute of Mineralogy and Geology of the University of Miskolc are working on the exploration of the primary and secondary sources and developing innovative preparation technologies of critical raw materials in Hungary. The research work showed in this article, focused on the recovery of critical materials from LCD TVs and monitors. There are high deviations in different literatures regarding to concentrations of critical elements in displays (e.g.: indium), probably because of the differences in production year, producers and recovery technologies. During the research - described in this study - a well specified sample of quite large amount of displays had been used. The exact place and shape of the ITO (indium-tin oxide) layer were determined by SEM analysis. The applied preparation technology was developed based on the results of our investigations and by technologies found in the literature. The developed process accomplishes two main parts: the mechanical preparation (mainly the liberation of different display layers, removal of liquid crystal) and the acidic dissolution of indium."

Jan 1, 2014

By Brabcova Z.

This contribution deals with bubble adhesion on particle surface which consists of three steps ? the liquid film thinning, the film rupture and expansion of the three phase contact (TPC). Our attention is devoted to the third step ? to the description of the TPC expansion. Three-phase contact line expansion can be theoretically described using hydrodynamic and molecular-kinetic models. Both of these models were originally developed for the interaction of the bubble with horizontal plane in pure water. Our experiments deal mainly with the interaction of the bubble with the inclined plane in the solution of surface active agents. It was proved experimentally that molecular-kinetic model corresponds also to these conditions and this model was used for the description of the TPC expansion. The model is based on the theoretical description of the bubble contact angle on the three-phase interface. These contact angles change dramatically from 180o to equilibium (Young) contact angle close to 90o. Modificated ADSA method is used for the calculation of the contact angle. This method utilizes the Laplace equation of the capillarity; the bubble profile and the contact angle are evaluated using the set of experimental points around the edge of the bubble. The comparison of the experimental and calculated bubble profile shows a good agreement. The aim of the project is to describe the process of the TPC expansion during the adhesion of the bubble with the diameter up to 1 mm. Inclined planes were used instead of an experimental solid particle. Our experiments were provided in the solution of surface active compounds. The process of the adhesion was recorded using high-speed digital camera and images were evaluated using the image analysis software NIS-Elements. Calculations were performed using the MATLAB software. Keywords: bubble-particle interaction, adhesion, three-phase contact, contact angle

Sep 1, 2012

By Cagri Emer

In conventional mechanical flotation cells, when the size of particles exceed a particular value, that is of the order of 100 µm for metal sulphides, the recovery of particles decline rapidly. It appears that the turbulence in the agitated vessel is sufficiently intense to rupture the forces of attraction between the particles and the bubbles, so the large particles are flung off the bubbles in the turbulent field. It has recently been suggested, that a fluidized bed would be a very favorable environment in which to contact bubbles and the particles. In a fluidized bed, particles are supported by rising flow of fluid, which separates them from each other and allows them to move freely while remaining close together. In this novel method, bubbles injected into the fluidized bed are able to rise through it, colliding with hydrophobic particles, transporting them to the top of the column where they can form a froth layer that overflows into a launder. The flow in a fluidized bed is generally slow and nonturbulent, and preliminary experiments have shown, that it is possible to collect mineral particles as large as 1 mm and coal particles as large as 5.5 mm. If the upper particle size limit can be extended, there could be significant reductions in the overall energy consumption in concentrators. Calculations show for example that if the top size for flotation could be increased from 100 µm to 400 µm, there would be a reduction in grinding energy of the order of 40%. It is therefore, important to study the mechanism of coarse particle capture in fluidized beds. In this work, the factors governing the capture rate of particles, particularly the particle and bubble size, the fluidization velocity and the superficial gas velocity have been investigated, and the results will be presented.

Sep 1, 2012

By M. McClintock

"High Pressure Grinding Rolls (HPGR) is increasingly being chosen for comminution circuits for its energy-efficiency for hard rock mining operations. Despite HPGR’s growing popularity, geo-metallurgy programs are still prohibitively expensive because of large sample requirements. Traditionally, sizing HPGR application requires a significant amount of sample, in the order of 1 to 10 tonnes, depending on the level of study and complexity of the resource. Therefore, engineering and design of HPGR circuits typically are reliant on few composites that are required to be representative of the resource and mine plan. Three bench scale HPGR test methodologies were developed in 2015 at NBK Institute of Mining Engineering at the University of British Columbia (UBC) capable of defining the energy size breakage relationship of pilot HPGR. These methodologies were developed to allow bench scale testing for different levels of study from PEA (Preliminary Economic Assessment) to detailed design and operations. The Piston Press test defines the energy size reduction relationship by measuring specific energy consumption and corresponding feed and product size distributions. The advantage of Piston Press testing is the small sample requirement of 5 to 10 kg. Small sample requirements allow multiple samples to be tested across a deposit. Piston Press testing allows extensive geo-metallurgy programs that can determine ore variability and inform in optimization and production planning. To date, the Piston Press methodologies have been validated on a pilot-scale HPGR unit located at UBC. Recently, testing was conducted to calibrate and validate the Piston Press test against full-scale HPGR on a gold sulphide ore deposit. The program included the collection of operational data with the respective HPGR feed and recycle sample. Sample collected was used both for Piston Press testing and HPGR piloting. This paper discusses the test-work and results as carried out during this program, using the aforementioned methodologies."

Jan 1, 2018

By Paulo Castillo, Cesar Gomez, Jaime Alvarez

Operations using flotation to produce mineral concentrates require testing of frothers to characterize their ability to preserve bubble formation size and to build a stable froth. Many techniques have been proposed to measure parameters associated with these two roles. These techniques focus, in general, on only one of these roles and are based on special equipment operated at conditions quite different from those existing in industrial cells and columns. Both roles have been simultaneously characterized in a laboratory flotation column, but the requirements associated with the installation and operation of one of these units, are a serious limitation for its use on-site. A technique based on the use of a laboratory mechanical cell, a common piece of equipment in operations, will have wider application. Establishing the ability of a frother to control coalescence by preserving bubble formation size is done through bubble size measurements as a function of frother concentration. Froth build-up and stabilization is associated with the amount of water carried by bubbles into the froth layer, which has been demonstrated to correlate with the gas holdup in the collection zone. Procedures devised for determining the critical coalescence concentration (CCC) from measurements of bubble size as a function of frother concentration, and the gas holdup by collection of water displaced from the cell by the presence of bubbles at different frother concentrations, were tested. Three analytical-grade frothers were utilized: a straight-chain (1-heptanol) and a branched (MIBC) alcohol and a polyglycol (PPG425). The results obtained at a standard set of conditions, demonstrated consistent differences between these frothers, and the ranking from least to most effective for reducing bubble size or decreasing water drainage followed the same sequences found when more complex frother characterization techniques are used.

Jan 1, 2014

By X. F. Cao

There was a large reserve of bauxite resources in China. And these resources were mainly the dias-pore-bauxite and contained plenty of aluminosilicate including kaolinite, illite and pyrophyllite. Reducing the contents of aluminosilicate would be significant to the using of Chinese bauxite resources. In this paper, from the single mineral flotation experiments, the surface properties and flotation beha-viours of aluminosilicate including kaolinite, illite and pyrophyllite, using dodecyl amine (DDA), N, N-dimethyl-dodecyl amine (DRN12) and N-dodecyl-1, 3-propane diamine (DN12) as collectors, had been investigated. The flotation results shown that the flotation behaviours of aluminosilicate had been influenced greatly by three amine collectors; and the effect was in the order of DN12>DRN12 >DDA. On the basis of FT-IR spectra and zeta potential measurements, the ionization of surface hydroxyl, as well as isomorphic exchange of surface ions, accounted for the mineral surface charges. And the mechanisms of interactions between the mineral surface and collectors mainly included two modes: electrostatic adsorption and hydrogen bonding; for the DDA and DRN>DDA. 12, the mechanism was mainly electrostatic adsorption; and for the DN12, the mechanisms of electrostatic adsorption and hydrogen bonding both existed. Results of quantum chemistry research shown that the collecting ability of amine collectors was greatly influenced by the electro-negativity of N in the amine molecules; and The |E(EHOMO| and ?E (HOMO-ELUMO) of N atom in DRN12 and DN12 were lower than that of DDA, and the positive charge of ?N group in DRN12 and DA12 were higher than that of DDA. All these calculation results could explain the collecting power of DN12>DRN12>DDA.

Jan 1, 2014

By C. Dorfling, S. Bradshaw, J. Eksteen, M. Khesa, C. A. Snyders

Titaniferous ores serve as a major feedstock for the production of a white titanium dioxide pigment, a titanium metal and several other titanium-based products. Such ores exist mainly as heavy mineral sands. Ilmenite is upgraded to intermediate products namely synthetic rutile and titania slag through the synthetic rutile route and the reductive smelting route respectively. Tronox KwaZulu Natal Sands (Pty) Ltd recovers high titania slag via the reductive smelting process while slag is used as a feedstock to the pigment industry and furnace dust from the gas cleaning plant is disposed as waste. Previous investigations have shown that such furnace dust can contain significant amount of titanium-bearing minerals. This study looks at the characteristics of the furnace dust obtained from Tronox KwaZulu Natal Sands and investigates a possible high temperature recovery route in detail. The furnace dust was examined by using x-ray fluorescence, x-ray diffraction, microscopy and laser-diffraction size analyses. The characterization work showed that the furnace dust was rich in titanium and iron, containing 49.4 wt% ??????2 and 29.5 wt% ????2??3. These oxides were associated with Si, Mn, K, and Al oxides as impurities. A Carbolite® vertical tube furnace was used to investigate the extent of formation of titania slag and metallic iron on a laboratory scale at 1500°C, 1600°C and 1650°C. The laboratory reduction tests revealed that the slag samples with an equivalent titanium dioxide content ranging from 70.9 -76.9 wt% at 1600°C and 1650°C could be obtained. The Fe content of the metallic iron samples produced ranged between 93.0 and 97.1 wt%. The experimental results were found to be in relatively good agreement with the FactSage simulations, both of which demonstrated the potential of producing a titania slag and a metallic iron from the furnace dust.

Jan 1, 2018

By M. Saghaeian, R. Hejazi, M. Farahani, M. Dehghani, A. Tohry

"Wet tailing dams of iron ore processing plants typically contain a significant amount of valuable minerals. In more recent years, due to the increase in iron’s prices and technological innovations, as well as the low energy consumption which required for processing of materials from tailings, dams can consider as potential valuable deposits. However, the production of iron concentrate from tailings is usually complicated where the high moisture content of the material, the high clay content and the presence of chemicals of processing such as flocculants, acids and flotation reagents, all make materials highly sticky which can be easily swollen. In the present paper, the optimization of operational parameters to recover ultrafine hematite iron ore from the wet tailings dams of the Chador-malu iron ore mine was investigated. The optimization of operational parameters, showed that with modification of the washing unit components for slurry making, the challenge of constraints from feeding the plant could be overcome. To decrease the magnetite content in the tail stream of the medium intensity magnetic separation (MIMS) and subsequently increase the efficiency, the orifice of the cleaner tail flow exit pipe was changed from 7 inches to 3 inch and yoke angle changed from 14 to 8 degrees. These changes increased mass yield by 3% and decreased the magnetite content in the final tailings to 1.2%. By recirculating the cleaner SLons of final tailings within the circuit, the solid percentage of the feed to rougher SLons decreased to around 15%, and as a result the matrices were not overloaded that easily, and mass yield increased to about 13% from 7%. All the above mentioned optimizations were achieved without significantly affecting the concentrate Fe grade."

Jan 1, 2018

By K. B. Venkatesh

In view of the importance of size reduction operations from the energy consumption point of view, during the past one hundred and fifty years a number of attempts have been made to develop a general energy-size relationship. However, to date it has not been possible to clearly define the scope of application of various laws proposed, though Bond law has been widely used with a moderate degree of success. It was, therefore, decided to carry out a thorough analysis of the batch ball mill grinding data available in the literature on several minerals that were ground under normal range of operating conditions. In particular, relationships proposed by Bond, Kapur, Voller and Morrell were examined in detail. It was found that the relationship proposed by Kapur in terms of the mean particle size provided a more accurate basis for estimation of energy. The value of the exponent of mean particle size in this relationship, a, is same as the exponent of the particle size in the expression for the grinding rate parameter: ki = Axia, provided the particle size distribution range corresponds to the self-similar or self-preserving regime. In this regime, mean particle size is proportional to the 80 percent passing size and size modulus. From the practical application point of view, it was possible to describe the variation of µ1 over limited, but significantly broad size range, using a constant value of a. Thus, by carrying out a few batches, grinding experiments over the size distribution range corresponding to the contents of the production mill, the applicable value of a can be determined. Keywords: energy-size relationship, ball mill, mean particle size, self-similar size distribution regime

Sep 1, 2012

By B. Rai

Processing of dolomitic phosphate ores remains one of the most challenging problems in phosphate ore beneficiation. The beneficiation plant at Jhamarkotra in Rajasthan, India for example is currently using a conventional double stage flotation process which involves first a fatty acids flotation to produce a combined dolomite-apatite concentrate (bulk concentrate) from associated silicate gangue. Dolomite is then separated from this bulk concentrate by flotation with fatty acids collectors and depressing apatite with phosphoric acid and sulphuric acid. This process requires addition of large dosages of reagents (H3PO4 and H2SO4) to depress apatite and to maintain highly acidic pH during flotation. Furthermore several cleaning and scavenging stages are needed to obtain the product of desired quality. We have developed and employed a molecular modelling based methodology of designing selective reagents for apatite-dolomite separation. We have been able to take into ac-count the differences in the distribution of calcium cations on these two surfaces in our design and hence develop novel phosphonic acid based depressants for apatite-dolomite separation with con-ventional fatty acids as flotation collectors. We have demonstrated the utility and power of molecular modelling based reagents design approach through this work on beneficiation of Jhamarkotra dolomitic phosphate ore using our novel phosphonic acids based depressants at pH?s close to natural pH. It was possible to reduce the MgO content of the ore from as high as 13.3 % to 1.5% in a single stage flotation. Our flotation separation results on Jhamarkotra ore with these new phosphonic acids based tailor-made depressants for apatite-dolomite flotation separation are discussed in this paper along with results of corresponding molecular modelling computations on the same system.

Jan 1, 2014

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 S. K. Kawatra, T. C. Eisele

"Coal-fired electrical power generation plants produce 56% of all the electricity in the U.S., burning approximately 860 million tons of coal annually. This results in the production of 58 million tons of fly-ash; 19 million tons of bottom ash and boiler slag, and 23 million tons of desulfurization sludge.s annually. These are a considerable disposal problem, and it would therefore be very valuable to be able to sell these residues and by-products as useful materials, rather than paying to dispose of them in landfills. However, utilization rates are currently very low, below 32% even for the most thoroughly commercialized combustion byproduct (fly-ash). This poor utilization rate is a result of the high impurity content of combustion byproducts, which makes them unsuitable for existing markets.Mineral processing techniques are useful for upgrading and utilizing combustion by-products. Fly-ash can be processed to remove unburned carbon, or utilized as a binder component in ore pelletization and agglomeration processes; bottom ash can be processed to produce certain aggregate grades; CO2 emissions can be sequestered using modified leaching techniques; and many scrubber sludge’s require processing before they can be used for producing gypsum products.The experiments described in this paper were carried out to study the application of mineral processing techniques to upgrading combustion by-products, particularly flue-gas scrubber sludge. A process was developed for upgrading unoxidized Flue-Gas Desulfurization (FGD) sludge’s by removing the primary impurity (unreacted limestone). A combination of hydrocycloning followed by froth flotation reduced the limestone concentration to as little as 1.7%, while recovering 66% of the sludge weight as a clean product. The recovered limestone was sufficiently concentrated that it could be recycled to the scrubber for more complete utilization."

Jan 1, 2003

By Yu. Gurevich, M. Teremova, I. Prokopev, A. Razvjaznaya, N. Algebraistova

"The objective of this work is the scientific justification and development of efficient and environmentally-friendly method of bulk concentrate preparation for selection with application of microbiological practices. This research suggests to apply Pseudomonas Japonica bacterial culture to the bulk concentrate before the selection circuit in order to clear the surface of sulphides from the xanthate skin. It is also suggested to apply bacterial consortium Ochrobactrum ?nthropi and Pseudomonas aeruginosa JCM 5962 for desorption of diesel residual concentrations. High-efficient and environmentally friendly method of copper-molybdene and lead-zinc bulk concentrate selection was developed based on theoretical and experimental research work with application of microbiological practices. In comparison with conventional methods (steaming, sodium sulphide washing) the above suggested bio-technological method of bulk concentrate preparation before selection cycle will allow to reduce material and power expenditures, and it is also environmentally friendly. INTRODUCTION High-efficient selection of sulphide bulk concentrate is gained exclusively after collecting agent is removed from mineral surface. Therefore, the problem of bulk concentrate preparing before the selection cycle is acute, since the further technological parameters of the subsequent separation depends on the effectiveness of pulp preparation. Existing traditional ways of bulk concentrate preparation. such as washing or steaming, are characterized by high energy and material costs in industrial conditions [1,2]. The microbiological treatment before separation of the bulk concentrate into different kind of concentrates appear one of perspective processes for treatment of bulk concentrates [3,4]. At the present time, the world practice of processing mineral raw materials demonstrates the wide application of technologies using microorganisms: bacterial leaching and oxidation, purification of industrial wastewater. This is due to the fact that biotechnological methods are environmentally safe, low-cost, and suitable for refining complex ores and raw materials of industrial origin."

Jan 1, 2018

By Y. P. Huang

Experiment results and operation practice on reutilizing old tailings dumped at SCIM (Shang-chang Iron Mine) of KISCO (Kunming Iron and Steel Corp.) are presented. In a production period over 30 years SCIM dumped about 8 million tons of iron ore tailings. For improving resources utilization instead of wasting, experiments on processing for reutilization of the old tailings are con-ducted. These tailings are fine size fractions of weathered iluvial ores rejected out by classification- des-liming in ore washing and dressing processes, containing TFe 21%~22% in hematite mainly and limonite occasionally. Their particle size distribution, in average, is of 72.26% minus 0.037mm and 30.88% minus 0.005mm. Existence of plenty of micro-fine particles makes the tailings refractory to process, resulting in poor metallurgy. The whole sample of the old tailings without size-classification is fed into experimental process. Slon-100 type high grads WHIMS (wet high intensity magnetic separator) with cyc-pulsing is adopted, which magnetism-focusing rod?s diameter is changed from 3mm into 2mm. Operational conditions of optimizing rougher separation tests are strengthened. An iron concentrate assaying 52.21% Fe at quantity rate of 18.39% and iron recovery of 44.40% is obtained. Operational practice shows that metallurgy and economy of the old tailings treatment are close to what achieved at experiments. It is estimated, therefore, that some 1.4 million tons of this iron concentrate may be recovered from the old tailings. This means that KISCO has moved its key one-step in re-mining and reutilizing the secondary resources, which would be a good demonstration in this industry. This is also of social and economic significance in response to China government?s request on reducing consumption of resources and establishing society with economy for achieving sustainable development.

Jan 1, 2014

By A. R. Videla, P. R. Brito-Parada, I. Mackay

"Linking results from laboratory scale experiments to industrial flotation behaviour is challenging. Typically, such experiments involve batch tests in which the system does not operate at steady-state, making it difficult to infer the effects that operating conditions have on flotation performance. In order to overcome this limitation a 4-litre recirculating tank was previously developed at Imperial College London. This tank is capable of reaching, and operating at, steady-state by recycling overflowing concentrate back into the feed. As well as instruments to control operating conditions, it is fitted with a system of sensors that allow the surface of the froth to be dynamically monitored. From this information, it is possible to measure the air recovery—a proxy for froth stability. Thus, this bench-scale tank can be used to understand the effect of differing operating conditions on flotation performance at steady state. However, so far, this cell has only been used to investigate idealised systems with only one or two species.Reprocessing of tailings dams is not only environmentally desirable but also increasingly economically feasible due to the declining head grades of primary deposits. There is also the added benefit of no further milling being required prior to flotation. However, the effects of fine and ultrafine particles on froth stability are not yet fully understood. In this work, the bench-scale continuous tank has been used for the first time to determine the flotation response of a complex feed, consisting of samples from a copper tailings dam, to changes in operating conditions. It was shown that the froth stability in the system is comparable to that of previous work and industrial tests, with a peak in air recovery being found at a superficial gas velocity of 1.13 cm/s. There is scope to optimize the froth stability of tailings flotation for enhanced metallurgical performance."

Jan 1, 2018

By Wenqing Qin, Yunfan Wang, Ximei Luo, Fen Jiao

In order to investigate the effect of nanobubbles on adsorption of surfactant on mineral surface, the nanobubbles on the surface of calcite with -37µm fraction in the sodium oleate system were controlled by pressurization and decompression to mixing vessel. Subsequently, the adsorption amount of sodium oleate on the surface of calcite were detected by ultraviolet spectrum at different stirring times and different pressures. At the same time, the nanobubbles on the calcite surface were imaged with atomic force microscopy (AFM). In addition, a homemade vacuum Hallimond tube device was used for the flotation of single mineral, and the grade and recovery of minerals in concentrate was used to determine the influence of the nanobubbles on flotation. The experimental results showed that a large number of nanobubbles were found on the calcite surface by AFM under the dissolved oxygen difference (DOD) condition of -4 mg/L. And a large difference in adsorption capacity of sodium oleate on the surface of calcite was observed under different air pressure conditions. It indicated that the ambient pressure had a certain effect on the adsorption of sodium oleate on the calcite surface, and this effect did not depend on the constant low pressure or constant normal pressure, but depended on the changing process of pressure. The single mineral flotation experiment results indicated the recovery of calcite under decompression condition (formation condition of nanobubbles) was 1.5-2 times that under constant normal pressure, and the flotation time is much shorter. Moreover, the recovery under constant normal pressure was greatly influenced by flotation time. In this paper, only one aspect of the effect of nanobubbles on mineral flotation was preliminarily explored. It was confirmed that after vacuum-pumping, the adsorption of sodium oleate on calcite surface could be increased, the flotation time also was greatly reduced and the recovery of calcite was increased.

Jan 1, 2018

By P. Latostenmaa, T. Hailemariam, M. Lundström, P. Halli

Doré process is unique way to treat precious metals in the copper electrorefining plant, since it uses anode slime as a raw material. In this pyrometallurgical process, also slag is produced together with Doré metal. However, the process is never ideal, and a part of metal is always lost into the slag. By using Doré slag as raw material for simply mineral acid leaching, some of the lost elements can be extracted and recovered, thus, increasing the sustainability and keeping metals in the circular economy loop. The Doré process itself is developed to convert almost all precious metals and PGMs in the Doré metal, leaving other elements into the slag fraction. The Doré slag consist of slag formers, such as borax and silica based minerals, but contain also traces of sealing materials. In addition, the Doré slag is rich in metals present in the anode slime, such as Cu, Bi and Sb, which are not converted into the Doré metal. There are only few published applications at the precious metal plants, where conservative grinding and flotation circuits have been utilized for the enrichment of valuable metals present in the Doré slag fraction (Godbehere, P.W., 1983; Segawa, C. and Kusakabe, T., 1996). However, the present study shows an alternative approach for the recovery of metals present in the Doré slag by hydometallurgical approach. The study focus on direct mineral acid (aqua regia) leaching of metals present in the Doré slag. The initial dissolved concentrations of Cu, Bi and Sb from Doré slag in the temperature range of 30-50 °C under oxygen purging with addition of 1 vol-% of H2O2 are presented. Chemical and mineralogical analyses were performed for the raw material, leaching residue, and leaching solutions in order to ascertain the leaching behavior of the metals of Bi, Cu and Sb.

Jan 1, 2018

By M. Kinnunen

Handling of municipal solid waste (MSW) and control of its potential resources is becoming increasingly important in modern society. The OECD (Organization for Economic Co-operation and Development) average on municipal waste produced in 2003 was that of around 570 kg per inhabitant. In European Union countries around half amount is of MSW landfilled. In Finland still 88% of MSW was landfilled in 2004. Since incineration reduces MSW volume significantly while producing heat energy, it has become one of the most common waste handling techniques. The shortcoming of incineration is however, that incinerated MSW is often not pre-sorted and it produces slags and ashes as side streams from which recovery of metals is difficult. This paper looks into possibilities of scrap metal recovery for recycling from municipal solid waste incineration (MSWI) bottom ash. In order to do that, a flow sheet of physical separation methods was developed and tested with Finnish rotary furnace MSWI bottom ash. In addition, an empirical model for estimation of the recoveries of scrap metals with physical separation methods for treatment of MSWI bottom ash was developed. According to the results of this study, for 1 Mt of incinerated MSW with 30% mass reduction, a minimum resource potential of 100 kt for magnetic metal scrap of roughly 24 % grade and about 19 kt of non-magnetic metal scrap of roughly 65 % grade. In other words, 57 kg magnetic scrap and 12 kg non-magnetic scrap per inhabitant at the mentioned grades, respectively. Although wide variations of parameters affect the MSWI bottom ash quality, it can be said that a considerable amount of metals is drained into MSWI bottom ash. Results of this study show that from MSWI bottom ash significant material streams metal scrap can be reintroduced into the resource cycle which would otherwise be lost.

Jan 1, 2014