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By Leon Lorenzen, Nursen Guresin, Harald Muller

The development of mining projects from discovery, exploration to actual production is a complex and time consuming process. Often poor process plant performance can be attributed to the use of non-representative samples and inadequate and/or unsuitable metallurgical test work when designing flow sheets during project feasibility study stages and specifying process equipment. Samples not representing the ore deposit and inadequate test work may lead to increased project development costs, since expensive test work and engineering may have to be repeated. It should be noted that for higher level engineering studies, larger scale test work is recommended and is a requirement for feasibility level studies. This would apply even if the technology is considered mature and well proven, as each ore body may have its own unique characteristics that, if untested at a larger scale, could result in significant design shortcomings, which will have to be rectified at later stages of the project, usually at significant additional costs

Jan 1, 2014

By Peter Ay, Harry Pempel, Satya Narra, Mike Müller, Jens Markowski

"Within the next few years major changes in mobility are expected. Increasing numbers of electric powered cars, electrobikes and E-Scooters define the transport sector. Recently lithium based traction batteries as storage medium have led into matrurity of series production combining high electrical efficiencies with low weights and compact dimensions. Due to the relatively young development with lithium batteries utilization, only few investigation were conducted regarding their recycling. Conventional battery recycling processes can not be applied due to differences in design and chemistry. So an automated disassembly and processing procedure for lithium traction batteries has been developed in the R/D-project ""Li-WERT"". Instead of complete smelting of the batteries without pretreatment, an automated disassembly and specific treatment of the material streams was realised, adjusted to the needs of the subsequent recovery technologies. A higher quality, with reduced expenses for the separation of fine-grained or fused material mixes, can be obtained for the individual components. The automated disassembly using an industrial robot significantly reduces dangers for the operating crew. The selective disassembly and beneficiation allows full recovery of the fractions. The batteries will be disassembled to cell level by the industrial robot. Anodes, cathodes, and separation layers are isolated and processed. The technology is designed, that no waste is generated for disposal. The pelletised cathode coating and the other separated metals (stainless steel, copper, aluminum) can be used in respective metallurgical plants. Circuit boards and plug contacts are also coveted secondary raw materials for reuse. The process is modular and offers high flexibility, e. g. for new battery types/ sizes by quick adjustment of the robot and tool change. Adaptation to other cathode materials (e. g. Li[FePO]) is possible. After finishing the R/D-project, a pilot plant for demontage was realised in 2013."

Jan 1, 2014

By T. Suzuki

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

Sep 1, 2012

By L. Stamenov, H. Bouzahzah, S. Gaydardzhiev, D. Naumov

"The Chelopech epithermal arsenic bearing high-sulphidation, copper-gold deposit located in Bulgaria is often referred as the richest European gold deposit currently under exploitation. Key points from the flotation circuit of the processing plant have been sampled and selected physicochemical parameters measured. Plant survey has followed with selected samples being submitted to chemical and mineral liberation analysis (MLA). Quantitative analysis has enabled to link the flotation response of the main copper bearing minerals with the physiochemical parameters (Eh, DO, EDTA extractable Cu and Fe) being measured. Data from mineral liberation analysis have highlighted an important process-relevant information explaining the variable floatability in the various granulometric classes.The low chalcopyrite recovery could be linked to the non-sufficient amount of dissolved oxygen measured in the copper selective flotation circuit. Given the finely-disseminated copper bearing minerals, the observed copper losses inside the flotation could be also explained by the insufficient degree of liberation of the mineral grains. Suggestions for improvement in metallurgical recovery are therefore proposed.INTRODUCTIONThe Chelopech deposit is a high sulphidation (HS) volcanic-hosted epithermal gold-copper one (Bonev et al., 2002; Kouzmanov et al, 2009; Strashimirov, et al. 2002). It is considered as one of the largest and economically most important ore deposits in Bulgaria, and often is referred to Europe’s largest currently mined gold resource. It is located in the Srednogorie zone which falls within the central sector of the extensive Tethyan–Eurasian copper belt formed during Mesozoic–Cenozoic time along the southern margin of Eurasia. The Srednogorie zone has the features of a subduction-related, Late Cretaceous island arc, with development of a calk-alkaline to sub-alkaline volcano-plutonic magmatism and associated hydrothermal ore deposits (Bonev et al., 2002).Ore mineralisation occurs as veins, mineralised breccia, and massive sulphide replacements and disseminations. Three mineralisation stages have been identified at Chelopech deposit. An early pyrite–marcasite mineralisation (stage I), characterised by disseminated to massive pyrite followed and partly brecciated by enargite– luzonite and tennantite–chalcopyrite–bornite (stage II) mineralisation. The gold is met in ores belonging to the stage II. Sphalerite and galena veins characterise stage III, best developed below and adjacent to the pyrite–enargite– chalcopyrite ore bodies. Advanced argillic altered volcanoclastic rocks commonly host this mineralisation (Chambefort and R. Moritz, 2014)."

Jan 1, 2018

By N. Naude, W. P. Roux

"Traditionally minerals processing equipment, such as jigs, are studied by characterising the feed and products from these processes. With this approach important details on the mechanisms of a process can be overlooked since assumptions have to be made on the internal operations of the equipment. Positron Emission Particle Tracking (PEPT) is a non-invasive technique that can be used to track a particle’s movement inside a closed vessel. PEPT makes it possible to observe the inner workings of a process, providing new information that was unattainable only a few years ago. Jigging has long been considered as one of the most difficult mineral processing techniques to model, due to the complexity of the mechanisms contributing to the separation of minerals during the jigging process. In this investigation PEPT was used to study the particle flow inside a laboratory batch jig. The aim was to determine if the particle trajectories could provide new insight into the jigging and its mechanisms. Three dimensional particle trajectories were observed with spatial and temporal resolution high enough to see details of the individual pulses during jigging. It was found that the pulse height is very dependent on the position in the jig bed. The vertical component from the trajectories showed the rate at which particles move through the jig bed (stratification rate) and it was seen that the density of a particle affects the stratification rate more that the particle’s size and that the shape in the range that was tested had little to no influence. Other phenomena such as a circular flow pattern was observed inside the jig and it was found that smaller lower density particles are affected by this circular flow pattern which tend to disperse these particles throughout the jig bed. Visualising the flow inside a jig by means of PEPT has shown to be instrumental in the deeper understanding of the process."

Jan 1, 2018

By Carlos Collado, Oscar Jimenez, Francisco Diaz, Rodrigo Bernal, Carmen Salinas

Water is a strategic resource for the mining industry. The rising cost has forced the industry to become more efficient in their use, reduce and recycle waste as much as possible. The importance of having a reliable water balance is increasingly urgent, because the resource is scarce and vital to the sustainability of human life, animal and ecosystem. Conventional flowmeters can suffer disruptions or failures by corrosion, fouling, presence of elements in the water as acids, salts and suspended solids. Use of radiotracers is advantageous to determine fluid velocities that are transported through pipes, as they are detectable by means of the radiation emitted, the same way for surface flows, such as natural watercourses and drainage from tailings dams, fluorescent tracers are those with the best advantages. For velocity measurements in pipelines a Iodine-131 tracer solution, around 5 mCi was injected into the suction of the pumps. The technique used is the transit time between detectors at known distances and determining the time of passage of the radiotracer. For measurements of surface fluxes using the fluorescent tracer Rhodamine WT by tracer dilution technique, injecting the tracer at a constant rate and measuring it known concentration diluted downstream. This work has been performed in Minera Los Pelambres, located in the IV Region of Chile, measuring the flow rate pumped from 12 pools with 1-7 pumps operating, obtaining speeds of 0.56 to 2.62 m/s. In pumping wells three facilities have been measured at speeds of 0.111-0.223 m/s, plus six surface flows with flow rates of 8.45 to 357.2 L/s.

Jan 1, 2014

By C. R. Mambote

One of the processes developed for vanadium recovery from the fly ash of crude oil is through acid leaching. In the process, iron is one of the impurities that should be removed before vanadium precipitation, due to the fact that iron tends to co-precipitate with vanadium. The mechanism of iron precipitation is understood in terms of ferric hydrolysis, followed by the dimerization and subsequent polymerization of the crystalline iron compound. In order to develop a new approach for the fly ash processing, in the present paper the precipitation of iron from the liquor after the leaching process was studied with addition of NaOH or NH4OH in the presence of H2O2 or Na2C2O4 at 80°C. The objective was to investigate the feasibility of the selective precipitation which could be applied to vanadium and nickel recovery from the fly ash. The experimental results show the difficulties of removing iron by precipitation without co-precipitating nickel and vanadium.

Jan 1, 2014

By M. Gonzalez Fernandez

"If the final goal of metallurgy is the extraction of metals from a given ore, everyone knows that this achievement relies on many separation steps involving much more than a biphasic material made of metal and gangue. Nevertheless, still today, most of the design and follow-up of industrial processes only consider metal grades; in best case metal grades per size class. Working with such heterogeneous material, made of several minerals, with different grain size and texture, implies to consider finer ore models to be able to predict the behavior of material and the subsequent operation performances. Analytical tools are now available to provide such relevant and accurate data which are applied in geometallurgy. To achieve a true geometallurgical approach for process design, but also for optimization, accurate process simulation absolutely needs to combine these fine ore models with the corresponding unit operation models. Based on generic, but configurable, criteria of description and a hierarchical approach, the material modelling tool embedded in the USIM PAC process simulator provides the necessary flexibility to describe any type of ore with almost no limit in the level of details and associated physical properties that can be met in the mining industry. The simulation engine and the mathematical models of unit operations are designed to manage such a diversity of material modelling. The paper present various ore models and some of their applications in flowsheet simulation. It proves the interest of this detailed and advanced approach to accurately predict plant performances. INTRODUCTION Process simulation used for process design and optimization requires accurate unit operation modeling. During the last decades, main efforts of the different teams developing software simulators have been dedicated to those models for comminution and physical separations such as flotation or gravity concentration (Kojovic et al., 2012, Soni and Yoon, 2014). In most case, the ore is modelled with a size distribution and metal or mineral grades. A water phase is considered for wet processes. The association of unit operations and such material models generally allows, after some parameters adjustment, to achieve good agreement between experimental and simulated data. The use of the obtained simulator to test alternative configuration of circuits or settings of equipment devices can be accurate enough as far as the ore processed is close to the ore used for simulator adjustment. However, when the ore gets very different grades, coming from different mineral proportions or grain sizes, the simulation results can be of poor accuracy. Because any physical separations such as gravity, magnetic or flotation, do not sort metal and gangue but particles, made of minerals, containing metals, the only way to be accurate enough for allowing extrapolations, is to model particles. The phase model tools embedded in the USIM PAC process simulator gives this possibility. However, as such level of details are not always available for analyses, the tool has been designed with a high level of flexibility, to adapt the model to the available data. In this paper, the principles of this conceptual modelling tool are presented, and some application cases illustrate the material model flexibility and its interest."

Jan 1, 2018

By J. R. Cui

The production of electric and electronic equipment (EEE) is one of the fastest growing areas. This development has resulted in an increase of waste electric and electronic equipment (WEEE). In view of the environmental problems involved in the management of WEEE, many counties and organizations have drafted national legislation to improve the reuse, recycling and other forms of recovery of such wastes so as to reduce disposal. Recycling of WEEE is an important subject not only from the point of waste treatment but also from the recovery of valuable materials. Consumer electronic equipment (brown goods), such as television sets (TV), radio sets, and video recorders, are most common. However, recent work on recycling of waste electric and electronic equipment (WEEE) primarily focused on personal computer and printed circuit boards scraps. Based on a detailed characterization study of consumer electronic scraps, recycling of TV scraps oriented to recovery of metals is highlighted by utilizing air table separation, eddy current separation, and optical (metal) sorting process. The result indicates that a high recovery of copper could be obtained by utilizing an effective gravity separation process. The separation results reveal that air table separation is an effective technology to recover metals from consumer electronic scraps. By using a DGS table, approximately 90% of non-ferrous metals were recovered in the heavy product with a purity of 40%. Printed circuit boards and cables in TV scrap cause metals loss due to the fact that metals in printed circuit boards and cables are not liberated from plastics and ceramic materials. The study shows that eddy current separation and optical (metal) sorting process provide alternatives for recovery of metals from shredded TV scraps.

Jan 1, 2014

By Yuki Tsunazawa, Shuji Owada, Kazuki Tahara, Shinobu Ogino, Chiharu Tokoro

"Printed circuit boards (PCBs) are an important constituent of waste electric and electronic equipment (WEEE), and contain many electronic components with valuable, hazardous or both materials. Recycling of PCBs is an important subject not only from the treatment of waste but also from the recovery of valuable materials. Demand for rare earth metals is expected to accelerate because of their growing use in next generation high technologies. Since some of these metals are concentrated in a specific electronic component, for example, Ta in capacitors, a special and selective grinding such as parts detachment from the board is effective for the recycling of a part of rare metals. However, direct computer simulation method to investigate a comminution/detachment process of PCBs has not yet been established. In this study, our objective was revealing the mechanism of breakage phenomena in comminution / detachment process of PCBs using computer simulation. A special and selective grinding using an agitation mill promoted the removal of components from a PCB by detachment and was an effective method for the recovery of rare metals. Simulant PCBs on which some capacitors were solder-mounted were used for the comminution test using drum type mill with agitator. To describe this mechanism of the parts detachment process, a computer simulation using discrete element method (DEM) was conducted. Although only an indirect simulation using the spherical particle model was possible for part detachment and board breakage, the particle-based rigid body model could directly represent the behaviour of PCBs. Simulation results successfully corresponded to comminution experimental results."

Jan 1, 2014

By A. Buchanan, M. Mirnezami, A. L. Restrepo, J. A. Finch, M. S. Hashemi

Settling rate studies on slurries from Cu/Zn flotation plants occasionally revealed two aggregation maxima at pH 8-10 and 10-12. From measurements on sphalerite and silica suspensions the double maxima were replicated by Zn ions (pH 8-10) and Mg ions (pH 10-12) corresponding to the presence of zinc hydroxide and magnesium hydroxide, respectively. A combination of chemical and electrostatic bridging by the hydroxides is considered to be the aggregation mechanism.

Jan 1, 2003

By William Conger, Greg Schick

Grinding media consumption is a major cost variable in industrial mineral comminution circuits. Specifically, industrial SAG media consumption results from a combination of surface abrasion wear, media breakage, surface spalling and rejection size from the mill. Three main consumption rates; weight of media consumed per time, per kWh and per weight of ore ground are defined and compared. Recent industrial data has provided an opportunity to relate consumption in terms of weight of media consumed to weight of ore ground (g/tonne) and weight of media consumed per kWh of energy consumed (g/kWh) with SAG specific grinding energy consumed (kWh/tonne). Using relationships developed from this data it is possible to project SAG media consumption in future mineral comminution circuits.

Jan 1, 2014

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

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

Jan 1, 2018

By Y. C. Liu

Ningxiang-type iron deposit is a most important sedimentary oolitic hematite deposit in China. Its? detected ore reserves are 3.72 billion tons, which is 73.5% of all detected reserves, and there are about 10 billion tons of prognostic resources. It is considered as the ?poor mine? for a long time be-cause of its difficult prooerty. But based on the ore characteristics of different deposits, the technological characteristics of ore are different with great diversity in ore baring horizon, distribution range, deposit scale, ore petrology, ore mineral assemblage and iron content. Through the study of deposit features and technological mineralogy of different Ningxiang-type of iron deposits in China, and based on industrial types and natural types of ore deposits, we divide different technological types according the technological features of the ore such as mineral composition, particle size, dissemination, occurrence of useful elements and harmful elements, the main physical and chemical properties of mineral and geological conditions of deposits, etc, moreover, propose the different utilization, mineral processing technologies and product schemes for the different types of ore.

Jan 1, 2014

This study examines the surface alteration and flotation behaviour of synthetic moncheite, PtPd(BiTe)2, in the presence of pentlandite. The telluride minerals contribute around 20% ~ 30% and up to 45% of the PGM present in the Platreef ore and are considered to be slow floating as there is evidence of these minerals reporting to the tailings. It was proposed that oxidation products from other minerals and grinding media would affect the mineral surface composition and floatability thereby causing inadvertent depression of moncheite due to precipitating ions. ToF-SIMS analyses (time of flight secondary ion mass spectrometry) was used to characterise the mineral surface as well as the extent of surface alteration. Microflotation was used to deter-mine the hydrophobicity of the synthetic minerals. Conditioning of moncheite in the presence of pentlandite reduced the flotation response of the + 38 -106µm size fraction from > 99% to 56%. This was due to pentlandite dissolution products (iron and nickel hydroxy species) which formed overlayers on the mineral surfaces thereby inhibiting the adsorption of collector. In addition, further grinding of these samples, with and without pentlandite conditioning showed a negative effect on recovery due to the fineness of the particle size distribution and there was no advantage gained from any possible exposure of fresh sites in the sample.

Jan 1, 2014

By S. S. Indi, D. Santhiya, S. Subramanian, K. A. Natarajan

The interaction of sphalerite- and galena-adapted Bacillus polymyxa (B. polymyxa) cells with sphalerite and galena has been investigated through adsorption, electrokinetic and flotation studies. The amount of sphalerite-adapted cells adsorbed onto sphalerite and galena is found to decrease with increase in pH. On the other hand, the adsorption density of galena-adapted cells onto galena shows a feeble maximum around pH 8, and the amount adsorbed is marginally higher in the pH range of 8 . 11.5. In the case of sphalerite the amount adsorbed is higher in the pH range of 5 to 7. The adsorption density of both the adapted cells is higher for galena vis-à-vis sphalerite. Electrokinetic studies indicate significant surface chemical changes on the chosen sulphide minerals and the bacterial cells, consequent to microbe-mineral interactions. Selective flotation tests on a synthetic mixture of galena and sphalerite confirm that sphalerite could be preferentially floated from galena, using galena-adapted cells, but not with the sphalerite-adapted cells. The cells adapted to galena assay a higher polysaccharide content and are more hydrophilic, while the sphalerite-adapted cells have a higher protein content and possess greater hydrophobicity. Transmission electron microscopic studies have provided evidence in support of the differences between the cell surface characteristics of sphaleriteand galena-adapted cells. Possible mechanisms of interaction between the minerals and the bacterial cells are discussed.

Jan 1, 2003

By Masoud Askari, Ahmad Rafizadeh, Shahamat Rostami, Mohammad Qaredaqi

Gole - Gohar Iron ore mines located in Sirjan, Southeast of Iran, have more than 1 billion Iron ore deposit and this area comprises 45 % of Iran Iron reservoirs. The aim of Wet tailing processing line is recovering Hematite ore from wet tailing of Gole - Gohar iron ore processing plant. The Investigations of Hematite recovery plant showed that the recovery of Iron ore to concentrate in Wet Tailing Processing (WTP) line is very lower than that has been predicted, sampling, and designing of the process parameters are not accurate and designed magnetic field intensity is not reasonable for the recovery of Iron in form of Hematite in this line feed. Applying of MIMS in WTP separator and changes in circuit caused in overwhelming increase of Fe recovery, from 11 to 40%. Although recovery of WTP line was improved, but low recovery of this processing line and high content of Hematite ore in WTP tailing, made applying Wet High Intensity Magnetic separators unavoidable. Two kinds of WHIMS have tested for processing of WTP line tailing. Results showed that traditional Jones separator with grooved plate matrix, is more suitable to achieve a better quality of concentrate compared to Slon® separator.

Jan 1, 2014

By G. Y. Zhou

During Zijinshan copper heap bioleaching, pyrite was leached in plenty resulting in high ferric concentration in solution. It has affected bioleaching and extraction processing greatly. It results much acid and iron in solution and bad effect to extraction processing. The paper studied the influence factors in the course of pyrite leaching and ferric ion chemical oxidation, especially studied the redox potential for copper bioleaching so as to find key factors affecting the dissolution difference between chalcocite and pyrite. The results show that the redox potential is important factor. Copper and pyrite leaching rates are 95% and 11% respectively and there is great dissolution difference between them at redox potential 700 mV (SHE). During pyrite bioleaching, the indirect action of bacteria gives priority to bioleaching cooperating with the direct attack of microbial cells attached to the mineral surface. Redox potential is determined by ratio of ferric and ferrous, ferric in solution was supplied by the way of oxidation of T. f bacteria, sufficient bacteria concentration and active character were two vial factors of controlling redox potential. It is indicated that copper can be selectively bioleached during copper bioleaching by controlling redox potential of bioleaching. The conclusion will provide theoretic foundation on balance of acid and iron during bioleaching for copper of higher S/Cu ratio. The experinment proved that bacteria activation was decreased on condition of both low pH value and intermittent aeratation during bioleaching. It resulted that the oxidation velocity of ferrous ion was decreased and redox potential was controlled. The dissolution of pyrite was depressed. It would be possible to actualize selective leaching of secondary sulfide copper ore during bioleaching process.

Jan 1, 2014

By Y. X. Li

In order to control the pulp level in flotation column which has long time-delay and great inertia, and is difficult to establish an accurate mathematical model, a Fuzzy-PID dual mode controller is applied. This method takes advantage of both strong flexibility and good reliability of fuzzy logic and high precision of PID. With the very stable and reliable process instruments, the control system has a good control performance and results the stable control of flotation column.

Jan 1, 2014

By H. Hamza, M. R. MacIver, M. Pawlik, L. Malin

"Size and shape are important properties of aggregates formed in engineering processes and natural systems. Measurement of aggregate size or shape is a challenge when the solids concentration is beyond the gel point, ?? > ??g, when the aggregates are in contact and it is difficult to distinguish or segment individual particles in the network. This paper describes the use of a micro-computed tomography (micro-CT) method for the calculation of the aggregate volume fraction, ??, and a characteristic aggregate length, ??a, based on a 3D chord length measurement algorithm. These parameters can be used to quantify changes in aggregate and pore size during a compressive yield stress test to help understand the impact of flocculation and network structure on dewatering. INTRODUCTION In a thickener, flocculation is often used as a pre-treatment step and the final solids content of the underflow depends on the network strength and permeability of the bed formed by settled aggregates (Usher, Spehar, and Scales 2009). This paper describes the measurement and analysis of micro-computed tomography (micro-CT) of flocculated mineral sediments to obtain a characteristic length, ??a, of the aggregate and pore phases during a staged compressive yield stress experiment. This parameter may be used as an indicator of changes in aggregate and pore size to quantify material behaviour in solid-liquid separation processes that depend on self-weight compression or applied pressure. This analysis was carried out to help understand the effect of flocculation on aggregate structure and the thickening process as part of a broader research on the improved solid liquid separation of tailings produced in the oil sands industry.Aggregate properties The solids phase of an aggregated or flocculated suspension will eventually settle – if left undisturbed – under the influence of gravity. As settling of a flocculated suspension continues, the solids volume concentration, ??, may increase to the gel point or gelation threshold (Landman and White 1994), ??g, above which the aggregates form a network of touching particles, or space-filling structure (Kranenburg 1994). In the sediment bed, the aggregates are surrounded by fluid and occupy a partial volume fraction, ??, according to"

Jan 1, 2018