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By Alireza Javadi Nooshabadi, Kota Hanumantha Rao

Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by sulphide minerals during grinding was examined. It was found that pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite ((Zn, Fe) S), and galena (PbS) generated H2O2 in pulp liquid during wet grinding and also when the freshly ground solids are placed in water immediately after dry grinding. Pyrite produced more H2O2 than other minerals and the order of H2O2 production by the minerals was found to be pyrite > chalcopyrite > sphalerite > galena. The pH of the water influenced the extent of hydrogen peroxide formation with greater amounts of H2O2 produced at highly acidic pH. Furthermore, the effect of mixed sulphide minerals, i.e., pyrite-chalcopyrite, pyrite-galena, chalcopyrite-galena and sphalerite-pyrite, sphalerite-chalcopyrite and sphalerite-galena on the formation of H2O2 showed increasing H2O2 formation with increasing pyrite fraction. There is clear correlation of the amount of H2O2 production with the rest potential of the sulphide minerals; the greater the rest potential of a mineral the greater the formation of H2O2. This study highlights the necessity of revisiting the electrochemical and/or galvanic interactions between sulphide minerals, and interaction mechanisms between pyrite and other sulphide minerals in terms of their flotation behavior in the context of inevitable H2O2 existence in the pulp liquid.

Jan 1, 2014

By Tatyana A. Ivanova, Tamara N. Matveyeva, Anatoliy A. Fedorov, Tatyana V. Nedosekina, Valentin A. Chanturiya

An ingenious methodology purposively developed by the authors for comprehensive assessment of flotation properties, electrophysical characteristics and. crystal chemistry features of natural gold-bearing sulfide minerals of different origin has been used in this study. Examination of the elemental composition of the minerals, ion-molecular components of the liquid phase in suspensions, surface properties of sulfides and different flotation reagents sorption forms was performed using the methods of X-ray phase and spectral analysis, potentiometry, UV and IR spectrometry, computer image analysis, and computer simulation techniques. The role of isomorphous impurities in the formation of hydrophobic sulfhydric collector layers on mineral surfaces in complex ore processing has been elucidated. The parameters characterizing the variability of the Fe:S ratio in pyrite of different origin have been determined based on non-stoichiometry characteristics of natural gold-bearing sulfide crystals. An ingenious method of formatting and linear approximation of experimental data was used to find out the quantitative relationships between the impurity content, electrophysical characteristics, non-stoichiometry and floatability of pyrite from a number of different deposits. The effect of the impurity species present in sulfides on the characteristic pH value marking the floatability peaks as such and their trend of shift towards higher alkalinity has been revealed. A theoretical substantiation has been given to prognostic assessment criteria for processing characteristics of gold-bearing sulfide minerals with varying composition. New flotation reagents and advanced reagent systems which help to increase the contrast of processing characteristics for different gold-bearing sulfides, resulting in improved selectivity, have been developed. The mechanism of selective flotation of precious metal-bearing Fe and As sulfides achieved by using short-chain dithiocarbamates and a mixture of cyclic trithiocarbonate with oxyalkylsulfides has been analyzed.

Jan 1, 2003

By David Dreisinger

"The leaching of base and precious metal ores and concentrates continues to progress in both laboratory study and industrial application. These developments are being driven by the need to respond to difficult ores and concentrates that are not amenable to conventional treatment. In many cases alternatives are being developed to conventional treatment (e.g. Pyrometallurgy) for technical and economic reasons.In this paper, a brief general review of some new developments in leaching will be followed by a more detailed explanation of three process developments that have either been industrially applied or are expected to be applied in a short time frame. The three processes to be reviewed in detail are the Mt. Gordon Copper Process, the Anglo American Corporation/University of British Columbia Copper Process and the PLATSOL Process. These leaching processes operate at low (90°C), medium (150°C) and high (220°C) temperature and are successful in quickly and completely extracting metal values from ores and concentrates."

Jan 1, 2003

By David Dreisinger

"The leaching of base and precious metal ores and concentrates continues to progress in both laboratory study and industrial application. These developments are being driven by the need to respond to difficult ores and concentrates that are not amenable to conventional treatment. In many cases alternatives are being developed to conventional treatment (e.g. Pyrometallurgy) for technical and economic reasons.In this paper, a brief general review of some new developments in leaching will be followed by a more detailed explanation of three process developments that have either been industrially applied or are expected to be applied in a short time frame. The three processes to be reviewed in detail are the Mt. Gordon Copper Process, the Anglo American Corporation/University of British Columbia Copper Process and the PLATSOL Process. These leaching processes operate at low (90°C), medium (150°C) and high (220°C) temperature and are successful in quickly and completely extracting metal values from ores and concentrates.INTRODUCTIONThe process of leaching is widely used in hydrometallurgy to selectively recover a metal of interest from an ore or a concentrate. Leaching and by extension hydrometallurgy is well established in the recovery of copper (copper heap leach ? SX-EW), nickel (Moa Bay and Caron process), zinc (roast ? leach ? electrowin and zinc pressure leach), gold (cyanidation) and uranium (acid sulfate leach). Of course this success extends to many of the metals found in nature. Recently, the importance of hydrometallurgy appears to be increasing with hydrometallurgy viewed as an attractive alternative to both traditional mineral processing and conventional smelting/converting/refining. This increasing interest has led to intensive study and increasing application. Selected developments include:Copper ? the Mt. Gordon process and new concentrate processes such as INTEC, Activox, CESL, Dynatec, Total Pressure Oxidation, MIM Albion, BioCop, and the AAC/UBC Process.Nickel ? Voisey Bay process for hydrometallurgical treatment of Voisey Bay concentrate, HPAL processing of laterites at Murrin Murrin, Bulong and Cawse, atmospheric leaching of laterites, heap bioleaching of nickel sulfides by Titan Resources (Australia).Zinc ? establishment of zinc leach, solvent extraction and electrowinning technology for treatment of the Skorpion deposit in Namibia, new developments in atmospheric and pressure leaching, the Hydrozinc process.Gold ? development of a number of thiosulfate leaching processes for recovery of gold from refractory carbonaceous ores or concentrates."

Jan 1, 2003

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 B. McFadzean, P. E. Ngoepe, P. P. Mkhonto, J. Taguta

The adsorption of heterocyclic collectors such 2-mercaptobenzothiazole (MBT), 2-mercaptobenzoxazole (MBO), 2-mercaptobenzimidazole (MBI) and their derivatives on pyrite form a basis in understanding the flotation reactivity that may be applicable in a wide range of sulphide minerals. This study uses a computational and experimental approach to determine the heat of adsorption of MBT, MBO, MBI and modified MBT collectors onto pyrite surfaces. Computational calculations found that the adsorption energies were in the order: MBO > MBI > MBT. The heterocyclic collectors were adsorbed in their thiolate form on the surface. In the case of the pyrite (100) surface, the MBT adsorbed through the exocyclic sulphur atom, while MBO and MBI adsorbed through the exocyclic sulphur and N atoms onto the 5-coordinated Fe atom. The (111) surface was found to be more reactive and different adsorption mechanisms were predicted, where the MBT exocyclic sulphur atom bridged on the 5- coordinated Fe and surface 2-coordinated sulphur atoms, while the N atom adsorbed on the 5-coordinated Fe atom. In the case of MBO and MBI, dissociation of the exocyclic sulphur atom from the collector occurred with subsequent interaction with the surface 5-cordinated Fe and 2-coordinated S atoms. This resulted in the collector carbon atom adsorbing on the surface 2-coordinated S atom, while the N atom adsorbed on the 5-coordinated Fe atom. The adsorption of the modified MBT was found to be more exothermic than the MBT, which showed that introduction of a –CS2 group on the exocyclic sulphur atom improved the affinity of MBT on the surface, and was thus a better flotation collector. The computational results were supported by experimental enthalpy of adsorption measurements and microflotation tests. The chemistry of the heterocyclic thioamides is complicated by the fact that they can exist in a number of tautomeric and ionic forms at different pH’s. This is discussed in relation to the flotation and calorimetric data.

Jan 1, 2018

By A. V. Nguye, P. A. Harvey

Previous studies have reported that inorganic electrolytes can enhance floatability of coal. The research has shown that the enhancement, if any, is highly dependent on changes in solution pH, type of electrolyte, and electrolyte concentration. The reasons for this are still not clear. In this study the floatability of coal particles in mono and divalent salt solutions was investigated. The zeta potential and hydrophobicity of the coal was measured experimentally, and a modified Hallimond tube was used to determine the floatability of coal particles by single bubbles, where the collision efficiency was equal to unity. The experimental information was used in conjunction with the Hogg-Healy-Fuerstenau equation to quantify the electrical double layer interaction. It was found that for low electrolyte concentration (less than 0.1 M) solutions the flotation recovery of coal particles was less than that for distilled water, and decreased with increase in concentration. Conversely, at electrolyte concentrations above 0.1 M, flotation recovery increased with increasing concentration. Both of these results are consistent with previous observations, but are inconsistent with expectations when considering the possible influence of electrical double layer interaction. A possible mechanism, based on the existence of the pre-existing submicron-sized gas bubbles, known as bubstons (i.e. bubbles stabilized by ions), present in water in close proximity to the hydrophobic coal surfaces is discussed in line with the early observation of flotation improvements by microbubbles “nucleating” on hydrophobic surfaces. In particular, the dependence of the bubble-particle attachment efficiency on electrolyte concentrations supports hypothesis on the salt-dependent and ion-specific existence of bubstons. However, a theoretical explanation of the transition salt concentration (at about 0.1M) is deficient at present. The existence of these submicrobubbles in close proximity to hydrophobic surfaces is not trivial. They can (as can individual gas molecules or other solutes) mediate and extend the range and magnitude of the attraction between hydrophobic macroscopic surfaces. These bubbstons may explain the curious phenomena of the socalled long-ranged hydrophobic attraction measured with the Surface Force Apparatus and Atomic Force Microscopy, and the slippage at hydrophobic surfaces. Finally, the coalescence of bubbstons affects the rupture of liquid films at a very large thickness (over 100 nm), observed, but unexpected, by flotation chemists.

Jan 1, 2003

By Xumeng Chen, Yongjun Peng, Dee Bradshaw

Regrinding rougher flotation concentrates has become a common practice when processing low grade and complex ores. It not only reduces the particle size and improves mineral liberation but also modifies particle surfaces and pulp chemistry due to the strong electrochemical reactions taking place during regrinding. Therefore, the floatability of minerals in the subsequent cleaner flotation is influenced by the regrinding conditions. This paper presents the effect of regrinding conditions on the mineral floatability from both industrial studies in the plant and fundamental studies in the laboratory. Different regrinding conditions were considered, including grinding media, the electrochemical properties of minerals, pulp chemistry (pH, Eh, DO), and breakage mechanisms in tumbling and stirred mills. Results indicate that the selection of regrinding conditions and mill types should not only depend on grinding energy efficiency and liberation but also depend on the surface properties and pulp chemistry produced for effective mineral flotation and separation at the cleaner stage.

Jan 1, 2014

By M. Rudolph, E. Schach, M. Buchmann, T. Leißner, N. Krupko, U. Peuker, M. Kern

"In mineral processing, density and magnetic susceptibility are two very fundamental properties. For the beneficiation of valuables to produce a saleable concentrate a detailed understanding of these properties is essential. Especially when it comes to the processing of cassiterite, which is the main mineral for tin production, they become highly prominent. Due to the chemically inert character of cassiterite towards most industrial applied leaching agents, density and magnetic separation processes are mainly applied for its beneficiation. To guarantee an optimized utilization of the different operations not only cassiterite but also the different gangue minerals have to be considered. In this study, a skarn ore is characterized by density and magnetic susceptibility. Therefore, the material was first split into different density classes by heavy liquid separation. The obtained classes were further separated by their susceptibility to finally obtain a density-susceptibility matrix. For this purpose, an isodynamic separator was used. A more detailed characterization of the materials is done via gas pycnometer, magnetic susceptibility balance and vibrating sample magnetometer to estimate the characteristics of density and susceptibility for the various classes. Further, the determination of the chemical assay and the mineral intergrowth by mineral liberation analysis is used to generate a three dimensional database for detailed characterization of the present ore. The objective of this study is to estimate potential material streams for a modular processing plant via characterization of the material for the entire deposit by the two afore mentioned characteristic properties. The established multidimensional data matrix, enables predictions for the separation properties of the material and contributes to the characterization of the deposit within the context of geometallurgy."

Jan 1, 2018

"This research represents a shift away from empirical models that lock the industry into 50-year old inefficiencies with little response to operating variability. The mechanistic and intrinsically dynamic mill model under development steps up to a new paradigm using the latest computing capabilities and physical understanding of breakage and transport to transform predictive capabilities for design, optimisation and on-line control with variable feed. The milling process is broken down into discrete sub-processes, each of which can be modelled as an object in the whole model and in the model code. These objects can be upgraded or exchanged without having to rewrite or restructure the remainder of the code. Sub-processes include: feed into mill; transport along mill; presentation to impacting events; range of impacting forces; probability of being impacted in different zones in the mill as a function of particle size and density; suspension in slurry; and discharge out of the mill. The unit and processes surrounding the mill (feed and recycle conveyors, slurry pump and pipe, cyclone and recycle crusher) have also been modelled, in order to incorporate the effect of recirculating load coming from a cyclone or a recycle pebble crusher, respectively for ball mills or SAG mills. Each unit is modelled dynamically and PID controllers have been added to control pumping flowrate from sump and water addition for cyclone feed dilution. The paper demonstrates the predictive capability of a dynamic, mechanistic model and is used to test the sensitivity to the sub-processes, comparing different formulations and highlighting the aspects that require further development. Validation on pilot tests and application to industrial data is presented. This approach is currently undergoing industrial trial on sites, for use in on-line model-informed process control. Considerable further development is required to incorporate the full mechanistic structure planned for this model."

Jan 1, 2018

By B. Y. M. Bueno

Biosorption of heavy metals can be an effective process for the removal of heavy metals ions from aqueous solutions. In this study, the adsorption properties of Rhodococcus opacus biomass for Pb(II) and Cu(II) ions was investigated. The effects of initial pH, initial metal concentration and biomass concentration on biosorption efficiency were studied in a batch system. Results showed that the initial pH would play an important role in the Pb(II) and Cu(II) ions removal by R. opacus and affected the zeta potential of R. opacus. The equilibrium adsorption was reached with 60 min. The Langmuir and Freundlich models were used for describing of adsorption isotherm data. The maxi-mum adsorption capacities of biomass were determined as 94.3mgg-1 and 32.2 mgg-1 for the Pb(II) and Cu(II) ions, respectively. The experimental data fitted to pseudo second order kinetic model. Adsorption capacity of Pb(II) ions was found to be reduced by the presence of the other competing metal ions in the system. The FT-IR results of R. opacus biomass showed that biomass has different functional groups and these groups are able to react with metal ions in aqueous solution.

Jan 1, 2014

By Jonas Addai-Mensah

In this paper, the results emerging from the several basic and applied studies performed to provide fundamental understanding of the interplay between clay pulp chemistry, orthokinetic flocculation performance, particle interactions, applied shear and dewaterability of fine clay mineral dispersions are presented, reconciled, and discussed. Modification of pulp chemistry and behaviour was achieved by using kaolinite and Na-exchanged (swelling) smectite clay minerals, divalent metal ions (Ca(II), Mn(II)) as coagulants and high molecular weight, anionic polyacrylamide copolymers: carboxylate substituted (PAM A) and 2-amido 2-methyl propane sulphonate (PAM S) (PAM S), non-ionic polyacrylamide homopolymer (PAM N) and non-conventional, non-ionic polyethylene oxide (PEO) as flocculants. Clear links between pulp interfacial chemistry, particle interactions and dewatering behaviour, resulting from the influence of hydrolyzable metal ion, pH, temperature, polymer structure type and shear, are established. Optimum conditions for improved, orthokinetic flocculation performance of negatively charged clay particles, reflecting faster settling flocs (>10 m/h) comprised: (i) coagulation, (ii) moderate agitation rate, (iii) shorter agitation time and (iv) anionic rather than non-ionic PAM. The optimum flocculation conditions did not, however, have a significant impact on the final sediment solid content of 20 ? 25 wt%. Further application of shear to pre-sedimented pulps improved consolidation by 5 - 15 wt % solid. Application of the findings and new knowledge gained to real plant tails? case studies for marked improvement in dewaterability through thickening is demonstrated.

Sep 1, 2012

By J. Y. Xu

A mutant of Phanerochaete chrysosporium, which is capable of degrading lignin, was bred by ul-traviolet ray irradiation and this mutant strain shows high capability of degrading of lignite. The degradation ratio of original Yima lignite and nitric acid treated Yima lignite by this mutant are 37.6% and 51.62%respectively, whereas those by the original strain are 31.84% and 32.55% respectively. XRD and FTIR analyses of the lignite converted product show that its polymerization degree and average molecular weight are both greatly reduced. The content of the functional groups is also been altered.

Jan 1, 2014

By S. Gerl

Since Schönert, 1980 a multiplicity of scientists have dedicated themselves intensively to the scientific investigation of wet grinding in agitated media mills. The achieved research results led to a clearly improved understanding of the comminution mechanism in wet operated agitated media mills and in consequence also to clearly more efficient machines. In contrast to this the standard of knowledge on dry grinding in agitated media mills is still very small. The practical experience from numerous plants shows however that the transferability of knowledge from wet grinding to the dry grinding regarding transport phenomena and comminution behaviour, influence of the operating parameters and also wear is very limited. In the industrial application above all the continuous mode of operation is preferred. The main problem which has to be solved in agitated media mills is minor the comminution itself, than rather the question of the trouble free material supply and material extraction as well as the cooling of the mill. The agitated media mill MaxxMill® offers an innovative concept to overcome the feeding and extraction problem with its rotating grinding chamber, the eccentrically mounted agitators as well as the eccentric flow deflector with integrated material supply. Because of the pneumatic extraction of the ground materi-al cooling of the milling chamber is not necessary. On a MaxxMill ® laboratory mill with a 5 litre grinding chamber volume extensive parameter studies were carried out to study the influence of operating parameters on the continuous dry grinding of quartz sand. The test were performed in a continuous single pass operation without classification of the final product. Apart from the influence of the throughput rate on fineness above all the influence of the agitator and grinding chamber speed as well as the grinding media size was examined.

Jan 1, 2014

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 R. K. Dwari

The electrostatic beneficiation of coal is based on tribocharging characteristics of ash forming minerals and coal particles. The tribocharging of quartz, pyrite and coal particles contacted with various metals and polymeric materials have been measured and the charge acquisition is assessed through surface energy calculations from liquid contact angle data. The contact angles, before and after tribocharging of solids, are measured using Krüss tensiometer and Washburn?s method where the sample holders in tensiometer are specially constructed with tribocharger materials. The charge polarity and amount of charge acquired by quartz, pyrite and carbon with metal tribochargers were found in good agreement with the reported work functions of the contacting surfaces. The charge results with polymer materials differed from the work function values, presumably caused by surface contamination. The surface energy of quartz calculated by all the theoretical approaches in the literature showed that the tribocharging increases the surface energy. Both polar and non-polar components computed from Fowkes and Owens-Wendt-Rabel-Kaelble approaches dis-play that both these components increased after triboelectrification. However, the polar component divided into acid and base components, as in van Oss approach, manifest decreasing acid part and increasing base part. Since quartz charged negatively during tribocharging with metal surfaces and therefore accepted electrons, the determined acid and base surface energy components are consistent with charge transfer process. The results also elucidate an explicit correlation between the charges generated by powders and the surface acceptor (acid) and donor (base) electronic states and thereby the work functions. A novel fluidized bed tribocharger was designed and developed with internal baffle system for efficient contact electrification of mineral and maceral to produce high differential charging for efficient separation. The results achieved on coal with 45% ash content are presented and discussed.

Jan 1, 2014

By Ashish Kumar

High grade ore deposits in the world are fast depleting and the valuables in the low-grade ores are finely disseminated. The feed grade to flotation circuit is also declining. Attainment of suitable grind is preferred, which inevitably creates more fines of the gangue minerals to interfere with the flotation process because of the undue competition between the fines and the valuables for the collector ion adsorption. Besides the use of polymeric or long chain hydrocarbon depressants for the gangue mineral, microbial induced flotation also has potential to float minerals selectively. Thiobacillus ferroxidans and Thiobacillus thiooxidans adhere on the minerals to modify its surface properties and affect the minerals flotation acting as depressants. Hindustan Zinc has conducted laboratory studies to understand the adhesion of microorganism on the mineral surfaces and its impact on the selective flotation. The experiments were further designed to reduce consumption of depressing reagents for graphitic carbon, pyrite, and galena. Preliminary studies reveal that desired quality of concentrate can be achieved with reasonable recovery. Keywords: thiobacillus thioxidans, thiobacillus ferroxidans, bioflotation, microbial induced flotation

Sep 1, 2012

By V. Sheikhzadeh, M. Saghaeian, R. Hejazi, M. Zare

High Pressure Grinding Roll (HPGR) plays a major role in increasing specific surface area of iron ore concentrate for producing pellet feed. HPGR grinding mechanism implies that material be compressed between the two rolls, therefore layer of material must be able to resist required pressure for achieving suitable grinding conditions. In this study for determining a simple relationship between material pressure resistance ability and HPGR main design parameters, piston press tests were performed on different iron ore concentrate samples along with HPGR Blaine increasing tests. Piston press tests results showed that by decreasing moisture content, material pressure resistance increased and in constant moisture content this parameter will change based on material specifications. HPGR Blaine increasing tests results showed that by decreasing moisture content, HPGR specific throughput and working gap increased and in constant moisture content this parameter will change based on material specifications. For all of the studied samples at worst condition, we got the results including: HPGR delta gap equal to zero, specific throughput lower than 200 ts/hm3.According to the tests results, HPGR Applicability Index (HAI) can be introduced at four different class types from 1 (weak) to 4 (excellent). This index determines achievable specific throughput and possibility of using HPGR according to material specifications, i.e. for HAI 1-4 the pressure resistance is <90, 90 to<125, 125 to <150 and = 150 bar, respectively. Similarly for HAI 1-4 specific throughput is <200, =200, =220 and =250, respectively. So based on design moisture content, if concentrate HAI is 3 or 4, HPGR is a correct choice. For HAI 2, HPGR can also be used. But for a material with HAI equal to 1, HPGR is not a good solution. As a result in order to apply HPGR for HAI 1, material condition such as moisture or slime content should be decreased.

Jan 1, 2018

By L. S. Gertsch

The production of minerals for human use at locations other than the Earth is expected to ?advance ? human prosperity in ? ways that [do] not compromise the potential prosperity and quality of life of future generations? (Brundtland, 1987); in other words, sustainably. This paper examines the interaction of extra-terrestrial mineral production (ETMP) with the following sustainability imperatives: ? The sustainability of human activities on Earth; ? The sustainability of human activities elsewhere; ? Human survival in general, the ultimate sustainability goal. Some of the consequences of mineral production on Earth are widely considered to decrease the future prosperity and quality of human life. Examples include noxious by-products or wastes and unsettling economic up- and downswings. Moving mineral production activities to extra-terrestrial locations, where appropriate, will decrease many of its deleterious effects. Terrestrial mineral production presently is decreasing in some countries and increasing in others, moving from the cheaper and easier ores to more expensive, difficult materials. When the full costs of maintaining the terrestrial environment in a sustainable manner are included, total mineral pro-duction costs must increase. The cost of extracting mineral products from extra-terrestrial sources will be substantially higher, especially in the initial phases, but as the full costs of terrestrial production increase, at some point in the future (different points for different minerals), the curves will cross (Fig.1). This will occur at different points for different materials, a process whose prediction will be complicated by substitution of cheaper materials for some uses as prices of the original material rise. In summary, mineral products from extra-terrestrial sources will tend to increase the sustainability of human civilization, once steady state has been reached.

Jan 1, 2014

By Elisabeth Schmidt

The conventional Canadian oil sand processing, the Clark Rowe process, is associated with many risks for the environment and high energy costs. To recover the bitumen from the oil sand (tar sand), large quantities of water have to be heated up and mixed with caustic soda and the oil sand. During this process, tailings with stabilized clay colloids are formed and dumped in tailings ponds. To avoid these disadvantages, a new, non-aqueous extraction process is to be established. Organic solvents are used instead of water and caustic soda to mobilize the bitumen from the sand-clay mixture. Pressure filtration, washing and steam pressure filtration are part of the new concept. A mixture of organic solvents and the oil sand is first pressure filtrated in a nutsch filter until a saturation level of one is obtained. After the cake has been formed, the filter cake is washed with organic solvent to flush the bitumen loaded solvent out of the cake. The following steam pressure filtration mechanically and thermally removes the remaining volatile components of the solvents from the filter cake. The filtrates from the pressure filtration, the washing phase and partly from steam pressure filtration are subsequently thermally treated to recover the organic solvents and obtain a higher bitumen concentration in the mixture. This mixture is then lead to an upgrader to win synthetic crude oil (SCO). The recovery of bitumen in the conventional hot water extraction process based on the Clark Rowe process can, in highly optimized plants, achieve between 88 and 92 %. Variation of oil sand properties leads to an actual range of between 80 and 90 % of bitumen recovery. With the alternative process based on organic solvents, the bitumen recovery exceeds the recovery of the conventional process by up to 16 percentage points. The composition of the two organic solvents in the first step of forming a suspension with the oil sand is important. The aromatic component is crucial for liberating and solving the asphaltenes, which tend to flocculate. The order of the two components of organic solvents is also important in the washing step. The paraffinic component is essential to achieve successful steam pressure filtration with respect to fast steam breakthrough and a filter cake free from organic compounds, as a result of its lower boiling point. Keywords: oil sand, filtration, organic solvents, pressure filtration, steam pressure filtration, filter cake washing

Sep 1, 2012