查看更多>>摘要：In mineral processing, ceramic balls have first been applied in secondary mill of the two-stage grinding circuit, showing great positive effect on the grinding process. This study evaluated the impact of replacing steel cylpebs with ceramic balls on the grinding effect, circulating load, classification effect, and the change of the particle size distribution and the distribution of valuable mineral (tungsten) in grinding products. The results obtained indicated that the particle size distribution of grinding products has been obviously improved, creating a reduction not only in the overall particle size, but also in the phenomenon of overgrinding (10 mu m). Reflected in the final product, the distribution of tungsten in the range of-74 + 10 mu m increased, while the distribution of that in the range of-10 mu m decreased. This is largely to the larger specific surface area created by ceramic balls in comparison with the steel cylpebs. Additionally, it is observed that circulating load was reduced by one-third, and the classification effect has been improved in secondary grinding circuit. According to the verification of grinding circuit model, the results revealed that the decrease of circulating load and the increase of classification effect is direct related to the improvement of grinding effect, and also presented that the secondary mill now has more reserved space for grinding based on the difference of relative capacity of the two media. Furthermore, it is worth mentioning that the application of ceramic balls in tumbling mill is exceedingly economic, given that the power consumption of the tumbling mill has been reduced by 38.5%, and the wear consumption of the grinding media by 60%.
查看更多>>摘要：Redox potential (Eh) control plays a significant role during sulfide mineral flotation by influencing the reactions on the surface of the minerals and accordingly the flotation behaviour. In this study, the metallurgical performance of typical copper sulfide minerals, molybdenite as well as gangue minerals (e.g., pyrite, tennantite, and enargite) under different pH and Eh conditions of the flotation cell were investigated. The copper and molybdenum processing plant at the Sungun complex-Iran were selected as a case study. For this purpose, Eh of flotation cells of phases 1 and 2 of copper and molybdenum processing circuits - Sungun complex - were measured by off-line method. After performing chemical analysis, the mineralogical study of the input load and products of each of the aforementioned flotation circuits in the rougher, cleaner, re-cleaner, and scavenger stages was performed. Based on the results, the potential in cells of phases 1 and 2 of copper concentration plants is in the range of -60 to-100 mV; and for the molybdenum plant, is in the range of -500 to-700 mV. The potentials of more than -100 mV in the phases of copper concentration plants have created suitable conditions for the separation of copper sulfide and molybdenite minerals from gangue minerals, especially pyrite. Adjustment of Eh in the range of-500 to-700 mV in the molybdenum processing plant has also led to the depression of copper minerals and the flotation of molybdenite, resulting in the effective separation of these minerals. However, grade analysis and mineralogical studies indicate the misplaced copper minerals into tailings, the passage of chalcopyrite and pyrite to molybdenum concentrate, the misplaced molybdenite to copper concentrate, and also the presence of minerals containing harmful elements such as arsenic in copper concentrate. Eh fluctuations in phase 1 and 2 of copper plants, the interaction of copper sulfide minerals, especially chalcopyrite with pyrite (and the depression of pyrite in Eh more than-100 mV), are reasons for the misplaced copper minerals into tailings. The interaction of chalcopyrite and pyrite with molybdenite and the high flotation tendency of molybdenite at the potential of +600 mV is the main factor in increasing the Cu and Fe grade in molybdenite concentrate. The interaction of copper minerals with arsenic-bearing minerals and the similar flotation behavior of these minerals in the potential of the rougher cells of the molybdenum processing plant has increased the arsenic grade in the copper concentrate or molybdenum tailings.
查看更多>>摘要：The nature of the hydrothermal reaction between sphalerite (ZnS) and pyrite (FeS2) particles and copper sulfate (CuSO4) solution was investigated in this study. The effects of temperature (443-523 K), CuSO4 (0.08-0.96 mol/ L) and H2SO4 (0.05-0.6 mol/L) concentrations, reaction time (1-120 min), stirring speed (40-100 rpm) and particle size (10-100 mu m) on the conversion of sphalerite and pyrite were studied. The ZnS conversion was significant already at 443 K and the most complete conversion was observed at T > 503 K after 120 min of treatment. For FeS2, conversion of about 50 % was achieved only at T > 523 K. It has been experimentally shown that the FeS2 treatment is a multistage process as the analysis of reaction kinetics suggests. The shrinking core model (SCM) was applied for describing the kinetics of the conversion process. Two stages of minerals' transformation were conditionally identified: 1-600 s (Stage 1) and 1200-7200 s (Stage 2). Stage 1 is responsible for primary interaction between the minerals and CuSO4 solution on the surface of the solid and the formation of a thin layer of Cu1-xS sulfides, while in Stage 2 a denser layer of Cu1-xS forms, which indicates a diffusioncontrolled step. The reaction orders with respect to CuSO4 and H2SO4 as well as activation energies were calculated for the hydrothermal treatment of ZnS and FeS2 with CuSO4 solution, respectively for Stages 1 and 2. The reaction mechanisms in both stages were proposed, and some inconsistencies that were reported in previous studies were explained.
Hoque, Mohammad MainulDoroodchi, E.Jameson, G. J.Evans, G. M....
15页
查看更多>>摘要：In flotation, interactions of bubble-particle aggregates with turbulent flow structures in the liquid medium result in particle detachment. This study aims to simulate this phenomenon involving a bubble-particle aggregate (bubble diameter ~& nbsp;3 mm and particle diameter ~& nbsp;314 mu m) interacting with a turbulent flow structure manifested as a confined vortex in a square cavity connected to a square cross-section channel. An interface resolved three dimensional (3D) computational fluid dynamics (CFD) model was developed to quantify the bubble-vortex interaction dynamics over a range of channel Reynolds numbers. The CFD model produced a good agreement with the experimentally measured vorticity magnitude, local energy dissipation rate, and bubble motion. It was shown that a bubble-particle aggregate could be captured within the vortex by suitably varying the channel Reynolds number, eventually leading to particle detachment. A separate force balance analysis was performed to determine a criterion for particle detachment utilising the CFD model predicted vorticity and local energy dissipation rate. It was shown that a critical local energy dissipation rate ~& nbsp;1.59 m(2)/s(3) was required for particle detachment to occur, which was also verified experimentally.
查看更多>>摘要：After more than a century applying flotation to the mining industry, two completely different strategies have been introduced for processing purposes. One is the classical approach viz. grinding ores to a certain extent (fine particles) and floating them via conventional mechanical and pneumatic cells i.e., Jameson, ImhoflotTM and RefluxTM. This strategy continues because mines face declining cut-off grades, complex and poly-mineralized ores, and they are required to achieve an acceptable degree of mineral liberation. The other school of thought deals with coarse particle processes mainly owing to the low energy requirements, that includes SkimAir (R) flash, fluidized bed and HydroFloatTM cells. There is no study in the literature to comparatively present the recent developments of flotation apparatuses versus the conventional mechanical cells. To cover this knowledge gap in the literature, the present paper endeavors to critically evaluate these concepts from several points of view, including existing technological advancements, water and energy usage, kinetics, and circuit design. A brief introduction of advanced technologies, along with their applications is presented. The data from literature and case studies showed that the Jameson, ImhoflotTM and recently developed RefluxTM flotation cells can be very effective for recovering fine particles owing to their specific hydrodynamic designs, intensive energy dissipation rate and generation of micron-sized bubbles (100-700 mu m). Very low (less than a few minutes) mean particle residence time, high gas-hold up (ca. 50-70 %), no agitation and high efficiency of particle-bubble collision were identified as their main advantages compared to traditional mechanical flotation cells. In addition to their common applications in cleaner stage, these cells were used in pre-flotation and scalping (producing final concentrate from the rougher feed) duties. Their main challenges were recognized as relatively unclear procedure on their scale up/down, optimization and simulation. The HydroFloatTM cell was indicated as a promising technology for recovering coarse particle fraction sizes by taking advantage of the fluidized-bed concept with plug-flow dispersion regime, high particle residence time, and limited cell turbulence. We finally concluded that fine particle flotation may remain as the main focus of re-processing tailings dams, while coarse particle treatment should be the focus of this century to reduce total energy consumptions.
查看更多>>摘要：Thiosulfate is an eco-friendly gold lixiviant that is promising to replace the highly toxic cyanide. Copper is a conventional catalyst in accelerating the rate of thiosulfate leaching of gold, but it causes high thiosulfate consumption and complex gold recovery process. Attempts on the replacement of copper by other transitional metals such as nickel, cobalt and iron have been made to address the two issues. Among the catalysts, iron is cheap with great potential of development and industrial application. Few research has focused on the thermodynamics for iron-based thiosulfate systems. In this paper, a systematic thermodynamic analysis on the thiosulfate leaching of gold catalyzed by Fe3+/Fe2+ and the ligand of EDTA(4-), oxalate (ox(2-)), cyanide (CN-) or citrate (cit(3-)) is conducted by constructing a series of predominance area and speciation diagrams. Information on the stability, speciation, and redox behavior of iron species under various solution conditions are provided to better understand the complex solution chemistry and possible mechanisms for the iron-catalyzed gold thiosulfate leaching. The likely reasons for the high stability and low consumption of thiosulfate under the catalysis of Fe3+/Fe2+ complexes are also proposed.
Lee, YejinPark, HangilMatviychuk, YevgenHolland, Daniel J....
9页
查看更多>>摘要：In the present study, the previously developed frother concentration analysis technique based on the solid phase extraction process and the cryogen-free benchtop NMR is extended. We demonstrate that this technique can accurately quantify the concentrations of the most widely used flotation frothers such as methyl isobutyl carbinol (MIBC) and polypropylene glycol (PPG) type frother within 30 min even in presence of residual flotation collectors (e.g., diesel or ethyl xanthate) and inorganic electrolytes. It was also found that the present technique can determine the concentrations of individual frothers in frother blends in the simulated process water sample even in the presence of background chemicals. This technique has great potential for real-time measurement of frother concentration on-site as the whole process can be fully automated and does not require specialist staff to operate and maintain.
Dankwah, J. B.Asamoah, R. K.Zanin, M.Skinner, W....
6页
查看更多>>摘要：In this work, we investigate the influence of fluid density on bubble-particle detachment and coarse particle flotation performance. Detachment studies were carried out using an electro-acoustic apparatus in a dense liquid environment using a lithium heteropolytungstate (LST) mixture with subsequent flotation studies carried out in a micro flotation cell at varying fluid densities. Our results indicate that bubble load was inherently limited by particle surface area and weak particle-particle interactions at coarser sizes. Coarser particles tend to follow the detachment behavior of relatively finer particles at increased fluid density. We also found that flotation per-formance in terms of recovery, rate, and maximum floatable size can be enhanced by controlling fluid density within a stated limit beyond which detachment in the froth phase causes overall performance to drop.
查看更多>>摘要：Metals from low-grade sulfide ores, electronic waste and mine tailings can be recovered using bio-hydrometallurgy. In this study, acidophilic microbial consortia of mesophiles and moderate thermophiles were applied in shake flasks as well as in stirred tank reactors (STR) to bioleach cobalt and copper from mine tailings in Chile. The mine tailings near Taltal contained considerable amounts of copper (similar to & nbsp;5000 ppm) and cobalt (similar to & nbsp;115 ppm). After adaptation of the mesophilic consortium, 38% of Co and 86% of Cu were recovered in 2-L STR at 10% solid load after 12 days bioleaching at 30 ?degrees C. In a mini-pilot test in 20-L STR at 15% solid load, Co and Cu extraction reached 49% and 83%, respectively. Improved metal recovery was obtained by using a moderate thermophilic microbial consortium at 42 degrees C, reaching 74% of Co and almost 100 % Cu in 2-L STR at 10% solid load. Low Fe dissolution below 14% for all tests was observed which may favor the downstream processing of Cu and Co. Together with the results from chemical leaching, the data indicated that Cu was mainly leached by sulfuric acid (acid leaching) while a high Co extraction required Fe(II)-oxidizing microbial activity (bioleaching).
查看更多>>摘要：In the present study, an effective and green method to recover silver, copper and lead from copper anode slime by carbothermal reduction and super-gravity separation was investigated. During the pretreatment process, 99.9% of selenium was removed from copper anode slime after sulphation roasting, and the valuable metals of lead, copper and silver were concentrated as the lead-silver-copper multiphase complex by carbothermal reduction. The influence of temperature on the reduction efficiency was studied and the results obtained were supported by thermodynamic analysis. Under the optimal super-gravity separation conditions of G = 600, T = 1423 K and t = 5 min, the filtrated lead-silver-copper multiphase complex and residual phases were obtained. Results showed that the yield of the filtrated Pb-Ag-Cu phase was about 83% and the recovery efficiencies of lead, silver and copper exceeded 98%, 96% and 89%, respectively. These residues could be recycled to the pretreatment processes. Finally, based on the phase diagram analysis and equilibrium calculations, the lead-silver and copper-silver phases can be obtained and this was demonstrated after super-gravity enrichment. This work confirmed that super-gravity technology was a feasible approach in the recovery of valuable metals from copper anode slime due to its significant advantages of high efficiency, simple operation, and being more environmentally-friendly.
NSTL
Elsevier