Wang L.,CAS Institute of Process Engineering |
Wu C.,Changsha Institute of Mining Research |
Ge W.,CAS Institute of Process Engineering
Powder Technology | Year: 2017
Gas–solid riser flows tend to be characterized by particle clusters that significantly affect the flow, the mass/heat transfer, and the reaction behavior. To account for the effect of such particle clustering on the mass transfer between gas and particles, we use a lattice Boltzmann model with coupled mass transfer to conduct fully resolved simulations for flow past arrays of particles with both homogeneous and heterogeneous structures. We find that the distributions of velocity and concentration among the particle arrays are both affected significantly by particle clustering, and that the computed Sherwood number for either the homogeneous or heterogeneous particle structure increases exponentially with Reynolds number. However, the Sherwood number for homogeneously distributed particles is 3–5 times greater than that for heterogeneously distributed particles. This further supports the case for particle clustering having a serious effect on the mass-transfer efficiency between gas and solid in processes that involve flow past arrays of particles. Finally, the feasibility of using the lattice Boltzmann method with our mass-transfer model to describe the mass transfer in a heterogeneous two-phase gas–solid flow is also discussed. © 2016 Elsevier B.V.
Liu X.,University of Science and Technology of China |
Liu X.,Changsha Institute of Mining Research |
Liu X.,National Engineering Research Center for Metal Mining
12th International Conference on Mining with Backfill 2017, Minefill 2017 | Year: 2017
In order to meet the need of efficient backfills in some low grade and hard-to-recover mines, a new backfilling method named short-processing tailing-storage-free filtration backfilling method was invented by studying on the quantity and concentration control of filtrated slurry, as well as optimizing of mine operating flowchart and cyclone clusters. No tailing storage is required for this system; as a result, tailings can be transported to cyclone clusters directly. Generally, the concentration and production rate of the downstream inside the cluster is between 68% to 72% and 69% to 72% respectively. This downstream then flow directly down to the continuous mixers for the mixing with cement, and ultimately, was filled into the voids through underground reticulation systems and boreholes. The installation time for this system has been reduced to 4 months, while the capital investment and operating cost are also reduced by 70% and 20% respectively. The strength of the filling body, with ratio of cement to sand 1:4, can reach up to 3.2Mpa in 28 days. Therefore, this system can be effectively integrated with the overall mining sequence, balance the mineral extraction rate and processing rate safely, hence to improve the profitability of the mine. Filling method is particularly cater for the mines which are complicated and hard-to-recovery, associated with poor external conditions and having some special requirements (Zhou, 2015 and Liu, X.S., 2015). The filtrated tailing backfilling method is the most widely used nonferrous mine filling method in China, and many Chinese mines have built the filtrated tailings cemented backfill system. This system utilize the cyclone cluster for tailing filtration, vertical tailing storage (most Chinese mines have two tailing storage silos which have volume between 800 and 2500m3), high pressure (wind) water for paste making, gravity-driving tailing inputs, continuous mixers, and ultimately fill the paste back into underground stopes. This backfill method is maneuverable and capable to produce high-concentrated and controllable filling paste which can always become sound filling body with high strength when solidified. However, it demand large capital costs of tailing storages and mixing systems, as well as lots of labour force; besides, the whole process is complex. In addition, the paste making would become hard when there are many coarser particles, as those particles always sink to the bottom and often lead to pipe plugging (Zhou, 2015 and Zhou, 2013). Copyright © 2017 by the Society for Mining, Metallurgy & Exploration Inc. All rights reserved.
Wang Y.,Hunan University of Science and Technology |
Shi Q.,Changsha Institute of Mining Research
Hangkong Cailiao Xuebao/Journal of Aeronautical Materials | Year: 2017
Four kinds of C/C-SiC composites were fabricated by isothermal chemical vapor infiltration (ICVI), and the 2.5D needle-punching carbon felt was taken as the preform. The volume fraction of carbon fiber in felt is 30%. The density of C/C-SiC composites is similar (1.87-1.91 g/cm3), while the weight ratio of SiC is decreased from 56% to 15%. The microstructure and phase composition of C/C-SiC composites were observed by SEM and XRD respectively. Friction and wear behavior of the C/C-SiC composites were investigated with the MM-1000 friction machine. The results show that the average macro hardness of matrix is decreased from 98.2HRA to 65.1HRA with the decrease of SiC content from 56% to 15%, and uniformity of hardness distribution is significantly decreased. Finally, by the analysis of microtopography of friction surface and wear debris, it is found that the superficial hardness has an obvious influence on mechanism of wear during braking process. The wear mechanism of the C/C-SiC composites transforms from grain wear to the combination of grain wear and adherent wear with the decrease of surface hardness. At the same time, the average friction coefficient and mass wear rate is increased obviously during breaking process. © 2017, Editorial Board of Journal of Aeronautical Materials. All right reserved.
Li S.-L.,Xiamen University |
Tang H.-Y.,Changsha Institute of Mining Research
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010
Experiments on acoustic emission (AE) characteristics of full-regime rock failure are carried out with stiffness test machine (MTS) under uniaxial loading, cyclic loading-unloading conditions to obtain the relations of stress-strain, stress-time-accumulative counts of AE, stress-time-AE rates. Based on the test results, the AE characteristics of loading process, unloading and reloading of loading-unloading process are analyzed. The results show that AE phenomena can apparently appear during the process of unloading. When being reloaded under the stress level not more than 50% of the peak stress, there are less or little AE counts occurring as long as the stress level is not more than the previous loading stress level, that means the Kaiser effect occurs. While reloading is made again on the stress-level of over 60% of the peak stress, there occurs obviously AE events, that is so-called the Felicity phenomenon. Rock samples show a large amount of AE events in the post-peak region for both loading and loading-unloading processes. And the results also show that there exists a relatively tranquil period phenomenon of AE for all samples of the style of AE abruptly increasing during middle stress stage.
Wei S.,Hunan University of Technology |
Xu X.,Changsha Institute of Mining Research |
Liu Y.,Hunan University of Technology |
Yang J.,Hunan University of Technology
Materials Chemistry and Physics | Year: 2011
A novel and facile method to prepare hydrophobic nano-silver colloid and aqueous coordinate was proposed. Chemical reduction of silver nitrate in a tributyl phosphate (TBP) solution containing polyvinylpyrrolidone (PVP) was conducted and stable hydrophobic nano-silver/TBP/PVP colloids were obtained. Adopting a phase transfer process, the as-prepared colloids can be diverted into an aqueous system to obtain hydrophilic nano-silver colloids. The resultant materials were characterized by digital camera, TEM, XRD and UV-vis spectra. The results show that the reaction can be accomplished fast at room temperature and the synthesized colloids can remain stable for a long time, and the mean diameter of silver particles is around 10 nm for both nano-silver colloids. The nano-silver crystalline is face-centered cubic (fcc) structure, and the UV-vis absorbance peaks are at 412 and 420 nm for aqueous nano-silver and nano-silver/TBP/PVP colloids respectively. © 2010 Elsevier B.V. All rights reserved.
Yin X.-G.,University of Sichuan |
Yin X.-G.,Changsha Institute of Mining Research
Sichuan Daxue Xuebao (Gongcheng Kexue Ban)/Journal of Sichuan University (Engineering Science Edition) | Year: 2010
The full failure, of loading rock samples and concrete samples were tested and its mechanics characteristics and Acoustic Emission (AE) characteristics were studied. The curves of mechanics characteristics and AE accumulative total and AE rate of concrete and rock failure were got. And the AE features including the relationships between AE and time, AE and stress were studied. By comparing the AE characteristics between rock, their different and similar AE characteristics were pointed out. The time-consuming phenomenon was discussed to both rock samples and concrete samples whose plastic deformation is obvious when stress is close to peak value strength at the process of one time loading. It was pointed out that the AE rate of those samples which have this time-consuming phenomenon will be declined and AE quietude will also appear in this stage. But for brittle rocks, neither this time-consuming phenomenon nor AE quietude will appear. In addition, the value of the parameter of time was analyzed and summarized in AE monitoring and studying. Time parameter should be paid more attention to in AE studying despite it could be ignored in general indoor rock mechanics experiment research.
Liu X.,Central South University |
Yu T.,Central South University |
Wei Q.,Central South University |
Yu Z.,Central South University |
Xu X.,Changsha Institute of Mining Research
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2012
Nanodiamond seeding is a well-established approach to enhancing the nucleation density in chemical vapor deposition (CVD) diamond growth. However, the effects of nanodiamond seeding are highly dependent upon the dispersion properties of nanodiamond particles, the solvent and the interaction between nanoparticles and substrate surfaces. Surface modification and fractionalization were employed to improve the dispersion of nanodiamond particles and separate those particles into a more narrow range of particle size. Mono-dispersed nanodiamonds with a ζ-potential and average particle size of -41.5mV and ~25.3nm, respectively, were then obtained. They can be charged on copper substrate without any contaminations. Two-dimensional self-assemblies of nanodiamond seeding were actualized. The density and homogeneity of nanodiamond particles which act as pre-existing sp 3 seeds shorten the incubation time of diamond nucleation to less than 30min. High quality of 750nm thick continuous diamond film was deposited on copper substrate in 60min. Furthermore, we calculated electrostatic interaction energy between nanodiamond particle and copper substrate by using the nonlinear Poisson-Boltzmann theory, and discussed interaction energy of nanodiamond-Cu substrate and nanodiamond-nanodiamond in the seeding process. © 2012 Elsevier B.V.
Chen W.,Changsha Institute of Mining Research |
Liu X.,Changsha Institute of Mining Research
Separation Technologies for Minerals, Coal, and Earth Resources | Year: 2012
In the iron ore of Yuanjiacun Mine, Taiyuan Iron and Steel (Group) Company Ltd (TlSCO), the main iron-bearing mineral is specularite, which features disseminated fine particle size distribution. In addition to quartz, the gangue minerals include a lot of refractory chlorite and amphibole. The influences of the slime on flotation time, reagent dosage and flotation results were investigated. The characteristics of selective separation of iron-bearing silicate minerals such as chlorite and amphibole from iron minerals were analyzed in detail. A practical process flow sheet was proposed for beneficiation of Yuanjiacun iron ore.
Chen W.,Changsha Institute of Mining Research
26th International Mineral Processing Congress, IMPC 2012: Innovative Processing for Sustainable Growth - Conference Proceedings | Year: 2012
The flotation efficiency of magnetic concentrate of the Anhui hematite ore, which includes a great quantity of iron-bearing silicates, has been studied through reverse flotation test with a new type of collector Fly-102. The results indicate that collector Fly-102 has a strong adaptability to the variation of temperature, when the flotation temperature is in the range of 10°C to 35°C, using collector Fly-102 can obtain good flotation indexes. Collector Fly-102 has a strong adaptability to the variation of the slime contents and grades of the flotation samples. When the content of slime and the grade of the flotation feeds are 30% and 55.63% respectively, under the condition that the temperature is 15°C, the open circuit flotation test was carried out with collector Fly-102. After one-stage roughing, one-stage cleaning and two-stage scavenging, a better result is got, the grade of iron concentrate reaches 67.12%, and the recovery of iron concentrate comes up to 84.15%.
He C.-S.,Changsha Institute of Mining Research
Caikuang yu Anquan Gongcheng Xuebao/Journal of Mining and Safety Engineering | Year: 2012
In this paper, to evaluate the cavability of ore rock comprehensively for guiding the block caving design, according to geological conditions exposed by engineering geological survey, the factors influencing the cavability of ore rock are studied by using multifactor comprehensive evaluation method. The results show that the comprehensive consideration on distribution law of the rock mass structure characteristics indexes can reflect the cavability of ore rock better. Finally, we classify the ore body cavability of one mining area in this paper, and find that the cavability of this mining area is between the levels of middle to better, which can provide an important guidance for the future work in mine.