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Peng Y.,Beijing University of Technology | Ge J.,Beijing University of Technology | Wang S.,Curtin University Australia | Li Z.,Changchun Gold Research Institute
Desalination | Year: 2017

A polyvinylidene fluoride (PVDF) hollow fiber module with a low packing density and the permeate orifices on one side was used in a direct-contact membrane distillation process (DCMD). Comparative tests were also performed using a highly hydrophobic polytetrafluoroethylene (PTFE) membrane and a low hydrophobic PVDF membrane with different packing densities. Under varying operating conditions such as the feed and permeate flow rates as well as temperature, the performances of the DCMD were comprehensively investigated. It was rarely found that salt breakthrough in an idle mode and air-vapor pocket in an operative mode could occur. Partial wetting was for the first time found tending to happen in the PVDF membrane in idle mode, which led to salt breakthrough. High feed temperature and flow rate accelerated partial wetting. On the contrary, the PTFE membrane prevented partial wetting and blocked salt permeation. The air-vapor pocket formation at the shell side was attributed to a high vapor flux and incomplete condensation. An increase in packing density and the inversion of permeate orifices could help the mixture of hot vapor and cold permeate eliminate the air-vapor pocket, which was for the first time observed and illustrated. © 2016 Elsevier B.V.


Ye Q.,State Key Laboratory Breed Base Of Complex Nonfer Metal Rsrc Cleaning Utilization In Yunnan Province | Ye Q.,Kunming University of Science and Technology | Zhu H.,State Key Laboratory Breed Base Of Complex Nonfer Metal Rsrc Cleaning Utilization In Yunnan Province | Zhu H.,Kunming University of Science and Technology | And 8 more authors.
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2013

Preparation of the reduced iron powder has been attempted with mill scale as the iron-bearing material and with wood charcoal as the reducing agent through microwave heating. The response surface methodology (RSM) is used to optimize the process conditions, with wood charcoal, process temperature, and holding time being the three process parameters. The regressed model equation eliminating the insignificant parameters through an analysis of variance (ANOVA) was used to optimize the process conditions. The optimum process parameters for the preparation of reduced iron powders have been identified to be the wood charcoal of 13.8 pct, a process temperature of 1391 K (1118°C), and a holding time of 43 minutes. The optimum conditions resulted in reduced iron powders with a total iron content of 98.60 pct and a metallization ratio of 98.71 pct. X-ray fluorescence (XRF) was used to estimate the elemental contents of the reduced iron powder, which meets the specification of the HY100.23 first-class iron powder standard. Additionally X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) analysis were performed and the results are compiled. © 2013 The Minerals, Metals & Materials Society and ASM International.


Li B.-L.,Jilin University | Shen X.,Jilin University | Chen G.-J.,Jilin University | Yang Y.-Q.,Jilin University | Li Y.-S.,Changchun Gold Research Institute
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2012

The Asiha gold ore deposit is located in the east part of the middle uplifted basement and granitic belt which is one important gold and ferro-polymetallic metallogenic belt in eastern Kunlun. The Early Indosinian diorite and biotite granite are the main ore-hosting rocks, while the NNE and NW-trending faults are major ore-bearing structures in the mine area. Vein I is one of the major auriferous veins, and is closely related to the minette spatially. Fluid inclusions in quartz crystals can be classified into aqueous two-phase and CO2-rich three-phase inclusion. Salinities of fluid inclusions contents of NaCl range from 1.83% to 8.13%, densities range from 0.69 to 0.87 g/cm3, and homogenization temperatures range from 155.3°C to 425.6°C. In mineralization stage I, fluid inclusions are characterized by low salinity, high-temperature, and CO2-rich. In mineralization stage II, CO2-rich fluid inclusions and gas-liquid two-phase inclusions coexist, which show the immiscibility or boiling characterized by CO2 escaping, and resulted in salinity increasing of the residual fluid. Fluid inclusions in mineralized stage III are the gas-liquid two-phase inclusions. Charteristics of fluid inclusions, accompanied with H, O, S isotopic compositions, indicates that the ore-forming fluid is mainly mantle-derived and additional meteoric water in the late stage. By analyzing of Laser Raman spectrum, the gas-phase in fluid inclusions chiefly make up of CO2, CH4 and N2. According to the diagram of isochore, the ore-forming pressure can be calculated to almost 98-132 MPa, the ore-forming depth ranges from 8.16-9.58 km. By contrast to other typical orogenic gold deposits, A conclusion can be safely darwn that Asiha gold deposit belongs to the mesozonal orogenic gold deposit, and the gold mineralization occured in the transition period from compression to extension tectonic environment during intro-continental orogenic movement in Early Indosinian.


Zhang Y.,Beijing University of Chemical Technology | Peng Y.,Beijing University of Chemical Technology | Ji S.,Beijing University of Chemical Technology | Li Z.,Changchun Gold Research Institute | Chen P.,North China Pharmaceutical Group Corporation
Desalination | Year: 2015

Membrane distillation (MD) is a promising desalination technology for water recovery from high-salinity solutions such as RO brine. Despite its great potential, MD has not been industrially realized because this technique generates a lower flux than reverse osmosis processes and exhibits a lower thermal efficiency than multi-stage flash. Enhancing the flux and thermal efficiency of MD is a major research focus for membrane researchers. In this study, the principles, transfer mechanism and thermal efficiency characterization of the MD process were introduced. Various factors affecting the thermal efficiency were analyzed. Several heat recovery techniques in the MD field that have been developed and widely employed were reviewed. •Membrane distillation (MD) is a promising desalination technology. © 2015 Elsevier B.V.


Fan H.,Beijing University of Technology | Peng Y.,Beijing University of Technology | Li Z.,Changchun Gold Research Institute | Chen P.,North China Pharmaceutical Group Corporation | And 2 more authors.
Journal of Polymer Research | Year: 2013

Hydrophobic symmetric flat-sheet membranes of polyvinylidene fluoride (PVDF) for use in vacuum membrane distillation (VMD) were successfully fabricated by the vapor-induced phase separation (VIPS) method using the double-layer casting process. To avoid the delamination that often occurs in double-layered membranes, the same PVDF polymer was employed in both the upper layer and support layer casting solutions. Solutions with low and high PVDF contents were co-cast as the upper layer and support layer of the membrane that was formed. In the VIPS process, the low PVDF content solution favored the formation of a layer with a porous and hydrophobic surface, whereas the solution with a high PVDF concentration favored the formation of a layer with high mechanical strength. The effect of the vapor-induced time on the morphological properties of the membranes was studied. As the vapor-induced time was increased, the cross-section of the membrane changed from an asymmetrical finger-like structure to a symmetrical sponge-like structure, and the surface of the membrane became rough and porous. The membrane subjected to the longer vapor-induced time also exhibited a higher permeating flux during the VMD process. The best PVDF membrane fabricated in this study had a mean radial pore size of 0.49 μm, and the rough upper surface produced a static contact angle of 145 with water. During the VMD process with a 3.5 wt.% sodium chloride (NaCl) aqueous solution, the best membrane that was fabricated produced a permeating flux of 22.4 kg m-2 h-1 and an NaCl rejection rate of 99.9 % at a feed temperature of 73 C and a downstream pressure of 31.5 kPa. This performance is comparable to or superior to the performances of most of the flat-sheet PVDF membranes reported in the literature and a polytetrafluoroethylene membrane used in this study. © 2013 Springer Science+Business Media Dordrecht.


Peng Y.,Beijing University of Technology | Dong Y.,Beijing University of Technology | Fan H.,Beijing University of Technology | Chen P.,North China Pharmaceutical Group Corporation | And 2 more authors.
Desalination | Year: 2013

Polysulfone (PSf) flat-sheet membranes with bi-continuous porous surfaces for direct-contact membrane distillation (DCMD) were successfully fabricated using a vapor-induced phase separation (VIPS) method. The present investigation revealed how the surface and cross-sectional morphology of PSf membranes and the desalination performance in DCMD were affected by exposure time, PSf content and relative humidity of air. In the VIPS process, an increase in exposure time led to a replacement of the bi-continuous top surface with a dense skin and to a large decrease in the permeate flux in DCMD. The best PSf membrane fabricated in this study had a mean pore radius of 0.32μm, water contact angle of 106.4°, the liquid entry pressure of water of 300kPa, and total porosity of 82.1%. During the DCMD process with a 35g/L sodium chloride solution, the best membrane produced a permeate flux of 30.0kgm-2h-1 and a very low conductivity of distilled water at hot-feed and cold-distillate side temperatures of 73°C and 25°C, respectively. The thickness of the hydrophobic layer of the membranes was first measured using the weight method, and its value was used in a simulation of the DCMD process. © 2013 Elsevier B.V.


Li Z.,Changchun Gold Research Institute | Peng Y.,Beijing University of Chemical Technology | Dong Y.,Beijing University of Chemical Technology | Fan H.,Beijing University of Chemical Technology | And 3 more authors.
Applied Surface Science | Year: 2014

The effects of the membrane characteristics and operational conditions on the vapor flux and thermal efficiency in a direct contact membrane distillation (DCMD) process were studied with a mathematical simulation. The membrane temperature, driving force of vapor transfer, membrane distillation coefficient, etc. were used to analyze the effects. The operating conditions that increased the vapor flux improved the thermal efficiency. The membrane characteristics of four microporous membranes and their performances in DCMD were compared. A polysulfone (PSf) membrane prepared via vapor-induced phase separation exhibited the lowest thermal conductivity. The PSf and polyvinylidene difluoride (PVDF) membranes were modified using SiO2 aerogel blending and coating to reduce the thermal conductivity of the membrane. The coating process was more effective than the blending process toward this end. The changes in the structure of the modified membrane were observed with a scanning electron microscope. Si was found on the modified membrane surface with an energy spectrometer. The PVDF composite and support membranes were tested during the DCMD process; the composite membrane had a higher vapor flux and a better thermal efficiency than the support. A new method based on a 3ω technique was used to measure the thermal conductivity of the membranes. © 2014 Elsevier B.V. All rights reserved.


Peng Y.,Beijing University of Technology | Ge J.,Beijing University of Chemical Technology | Li Z.,Changchun Gold Research Institute | Wang S.,Curtin University Australia
Separation and Purification Technology | Year: 2015

Membrane distillation (MD) is a promising desalination technology for water recovery from reverse osmosis (RO) brine. However, calcium sulfate as the major pollutant in RO brine concentrates induces scale occurrence in MD. Effective control of membrane scaling and cleaning of the membrane module are the key technologies for the industrialization of MD. In this work, effects of four anti-scaling and five cleaning agents on calcium sulfate scaling in direct contact membrane distillation (DCMD) process were investigated and discussed. It was found that membrane scaling and wetting was significantly alleviated with the addition of an effective anti-scaling agent. The flux recovery of a membrane with five cleaning agents was also improved and the flux recovery using a 2% EDTA-4Na solution was obtained as high as 92.8% at 77°C. © 2015 Elsevier B.V. All rights reserved.


Wang Z.-H.,Northeastern University China | Wang H.,Changchun Gold Research Institute | Li G.-F.,Northeastern University China | Yu F.-J.,Northeastern University China
Dongbei Daxue Xuebao/Journal of Northeastern University | Year: 2014

Using Z-164D as grinding aid, the Bond work index of ball mill experiments and the uniaxial compressive strength experiments of bauxite from Tianyang Guangxi were carried out separately. The results showed that compared with raw ore, the Bond work index of bauxite soaked with water and Z-164D solution are decreased by 1.05% and 3.79%, and the uniaxial compressive strength are reduced by 26.84% and 42.79%, respectively. The physical and chemical adsorption between Z-164D and bauxite surface are confirmed through the analysis of IR spectra and energy dispersive X-ray spectroscopy, and Z-164D cannot dip into bauxite inners. A function mechanism model of the effect of Z-164D solution on bauxite strength is built, where water and Z-164D promote each other to increase defects of bauxite and lower its strength.


Ge J.,Beijing University of Chemical Technology | Peng Y.,Beijing University of Chemical Technology | Li Z.,Changchun Gold Research Institute | Chen P.,North China Pharmaceutical Group Corporation | Wang S.,Curtin University Australia
Desalination | Year: 2014

Membrane wetting and fouling were studied using hollow-fiber polyvinylidene fluoride (PVDF) membranes to concentrate reverse osmosis (RO) brine in a direct contact membrane distillation (DCMD) process. The effect of the operating conditions, such as the feed temperature, the flow velocity and the feed solution concentration, was investigated. Membrane wetting was more significant at high feed temperatures, and the salts in the feed promoted membrane wetting; membrane wetting resulted in a decrease in the flux and salt rejection. A theoretical model was developed to simulate the DCMD process, and the results of the model were analyzed. The concentration factor significantly affected the flux and the electrical conductivity of the distillate. When the concentration factor (CF) was less than 3.5, CaSO4 did not crystallize because of high ionic strength and higher solubility of CaSO4 at the membrane surface than in the bulk solution; beyond CF of 3.5, membrane fouling was exacerbated because of CaSO4 crystallization. Membrane fouling was more significant at the higher of the two temperatures investigated for long-time DCMD operation: square CaSO4 crystals formed at 77°C, whereas snowflakes formed at 55°C. The permeate was lower in the divalent cations, Mg2+ and Ca2+, than in the monovalent cations, Na+ and K+. © 2014 Elsevier B.V.

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