查看更多>>摘要：Static leaching experiments were performed to detect the heavy metals release rule of stone coal waste rocks at different solution pH levels. Results showed that solution pH exerted a significant influence on mineral dissolution. As solution pH decreased, the dissolved quantities of minerals increased gradually. With leaching time progressing, the dissolved quantities of Cr and V at each experimental pH level increased almost all the way, while As and Cd dissolved quickly at first and then the dissolution decreased. The dissolved quantities of major elements in the stone coal waste rocks were also detected.Ca and Mg dissolution increased rapidly in the beginning and then decreased slowly; however, the dissolved quantities of Al and Fe were relatively low. The maximum dissolved quantities at a solution pH of 2 were observed in the following order: Ca (2695.65 mg/kg) > Mg (510.92 mg/kg) > Al (23.64 mg/kg) > Fe (11.55 mg/kg) > V (6861 mu g/kg) > Cr (1005.35 mu g/kg) > Cd (751.71 mu g/kg) > As (323.66 mu g/kg). It can be seen that the dissolution of the elements is not correlated with their total content in the stone coal waste rocks, but is related with their content in easily soluble fraction (F1). The stone coal waste rocks were found to exhibit a relatively high neutralizing power, in that, in the range of initial solution pH at 3-9, final leachate pH stabilized at 83-8.5. This neutralizing ability was conducive to precipitate newly dissolved heavy metals, thus was favorable for reducing the waste rocks environmental toxicity. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：Ball mill charge size distributions originally specified for Bond grindability tests to determine the Bond Work index (BWi) are not commercially available. Those proposed to date do not match all of Bond's (1961) original specifications of total ball mass, number and surface area. An alternative mill ball charge is proposed that closely approximates Bond's original total ball mass, number of balls and ball surface area.
查看更多>>摘要：Experimental studies on the influence of scraper movement on, the fluidization of air dense-medium fluidized bed (ADMFB) have been conducted. The maximum bed pressure drop is about 3% when the scraper speed changes from 0 to 0.5 m/s. The minimum fluidized velocity U-mf decreases as the scraper speed increases. At the same time, the bed density only declines by 3.7%, and the density standard deviation decreases significantly which is mainly caused by the horizontal motion of the medium. The separation tests indicated that the most appropriate scraper speed is between 0.1 m/s and 0.3 m/s and it was reasonable to move the scraper at the appropriate rate to get the better separation performance. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：Reverse flotation is an effective method for separating apatite from gangue minerals (such as dolomite) in collophanite ore. However, collophanite ore flotation using traditional fatty acid collectors is uneconomical because of the relatively high cost of the raw materials. In this work, saponified gutter oil fatty acid (GOFA) was used as the collector, and its effect on collophanite ore flotation and the mechanism of adsorption were studied. The results showed that Ca2+ is the active site for reaction with GOFA and initiates apatite flotation. The dissolution of Ca2+ from dolomite was found to be thermodynamically more favorable than that from apatite, and the relative abundance of Ca2+ enhanced the reaction of dolomite with GOFA. XPS analysis revealed that the interaction between GOFA and magnesium on the dolomite surface strengthened chemisorption. As magnesium is a major constituent of dolomite, but not of apatite, GOFA was selectively chemisorbed onto the dolomite surface. Closed-circuit reverse flotation tests using GOFA as the collector resulted in an excellent concentrate with 28.46 wt P2O5 and 0.65 wt% MgO, corresponding to a P2O5 recovery of 87.2%. GOFA was demonstrated to exhibit outstanding selectivity for dolomite in the reverse flotation of collophanite ore. The use of GOFA as an environment-friendly, cost-effective, and selective collector is expected to provide new insights into low-cost collophanite ore flotation. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：Co-reduction roasting of seaside titanomagnetite and blast furnace dust was investigated to maximize the use of these ores in Indonesia. This direct reduction process utilizes fixed carbon in BFD to reduce iron from BFD and titanomagnetite. X-ray diffraction and X-ray fluorescence analyses were performed to characterize the reduced iron powder. The influences of reduction conditions, such as reduction temperature and duration, C/Fe molar ratio, grinding fineness and fluorite dose, on the indicators of reduced iron powder were evaluated. Fixed carbon and volatile matter contents were lower in BFD than those in coal. However, reduction and separation of titanium and iron exhibited similar effects on reduction roasting. Results showed that the optimum conditions of roasting reduction included C/Fe molar ratio of 0.65, fluorite dose of 4 mass%, and roasting temperature of 1300 degrees C for 60 min. The reduced iron powder was obtained through two-stage grinding and two-stage magnetic separation of the roasted product The former contained 94.23 mass% Fe and 0.58 mass% TiO2 and showed total iron recovery of 87.62%. The latter contained 19.72 mass% Fe and 25.47 mass% TiO2, thereby providing prerequisites for titanium recycling. (C) 2017 Published by Elsevier B.V.
查看更多>>摘要：A novel method for Na2SnO3 preparation from SnO2 and Na2CO3 roasted under CO-CO2 atmosphere in a solid state has been successfully developed. In this study, the formation kinetics of Na2SnO3 was investigated. The formation of Na2SnO3 was controlled by the first-order interfacial chemical reaction at 800 degrees C under 10 vol% CO content; as the temperature increased to 850 degrees C-900 degrees C, it was controlled by the three-dimension (Ginstling and Brounshtein) diffusion through the product layer at the early reaction stage. The rate constant increased with the increasing of temperature. Furthermore, the rate controlling characterizations of three-dimension diffusion were also discussed. (C) 2017 Elsevier B.V. All rights reserved.
Moosakazemi, FarhadMohammadi, M. R. TavakoliMohseni, M.Zakeri, M....
9页
查看更多>>摘要：Different factors involving in grinding of ore cause various breakage mechanisms. These different mechanisms differ the morphology of ground particles. In this study, the effect of ball mill types, feed sizes, and ball surface area have been investigated on the morphology of ground quartz particles using MBL cruise optical microscope and Olympus E-510 camera. Measured two-dimensional particle projection was expressed mathematically such as circularity, roundness and aspect ratio by ImageJ software. >20,000 particles were morphologically measured for image analysis. Results show that circularity and roundness of ground particles are enhanced in an ordinary ball mill equipped with smooth liner (OBM). While higher aspect ratio of ground particles are achieved in cylindrical ball mill equipped with wavy liner (CBM). Consequently, the dominant breakage mechanism for OBM and CBM are abrasion and impact, respectively. Circularity and roundness values of coarse-grained ground particles are more than fine-grained particles. The increase of ball surface area causes the increase of circularity as well as roundness values and the decrease of aspect ratio value. (C) 2017 Published by Elsevier B.V.
查看更多>>摘要：The effects of alkaline solution and calcined clays on vibrational spectra and mechanical properties were studied on geopolymer samples prepared from two alkaline solutions, calcined clays and three metakaolins. Structural evolution of the prepared geopolymers was characterized using FTIR spectroscopy and compression tests. Our results indicated high positive correlation between reactivity and compressive strength of the studied samples. Commercial potassium silicate and laboratory prepared k-silicate solutions were used to assess their effects on the prepared geopolymers. It was also observed that various secondary phases appeared, causing a slight change in the species' reactivity. Finally, it was concluded that changing alkaline solution and calcined clays decreased the mechanical properties, but increased the FTIR shift values. However, further work is needed to study the effects of alkaline solutions and natural clays from Tunisia on the properties of the prepared geopolymer. This is compulsory for prospective application of those products in various industries. (C) 2017 Elsevier B.V. All rights reserved.
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