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Table of Content
05 August 2014, Volume 65 Issue 8
    CIESC Journal(HUAGONG XUEBAO)Vol.65 No.8 May 2014
    2014, 65(8):  0-0. 
    Abstract ( 262 )   PDF (1961KB) ( 185 )  
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    Dissolution kinetics and thermodynamics of Mg-Al hydrotalcites
    XU Sheng, LIAO Mengchen, ZENG Hongyan, ZHU Peihan, ZHANG Zhiqing, HUANG Qingjun, LIU Xiaojun, ZHANG Wei
    2014, 65(8):  2863-2868.  doi:10.3969/j.issn.0438-1157.2014.08.001
    Abstract ( 768 )   PDF (531KB) ( 724 )  
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    The dissolution of Mg-Al hydrotalcites in aqueous solution and its mechanism were investigated, with the dissolution kinetics and thermodynamics at different temperatures and pH. The kinetic model with the outer diffusion and chemical reaction control can be used to describe the dissolution process appropriately, with different controlling steps in various pH ranges. In the pH range from 1.0 to 3.8, the hydrotalcites dissolve completely and the dissolution rate decreases as pH increases, with the dissolution controlled by desorption. In the pH range from 4.2 to 9.4, the hydrotalcites partly dissolve, independent of pH, with the dissolution controlled by surface exchange reaction. On the other hand, the Gibbs free energy change of the dissolution reaction from the Mg-Al hydrotalcite is estimated as 29.516 kJ·mol-1 at 298 K. The result is consistent with the experimental evidence.
    Heat transfer coefficient between a freely moving graphite sphere and a fluidized bed
    CHAO Junnan, LÜ Junfu, YANG Hairui, ZHANG Man, LIU Qing
    2014, 65(8):  2869-2875.  doi:10.3969/j.issn.0438-1157.2014.08.002
    Abstract ( 627 )   PDF (570KB) ( 294 )  
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    The heat transfer between a dense bed and freely moving coal particles is of great significance for designing and operating a circulating fluidized bed (CFB) boiler. In this study, heat transfer coefficients were measured for graphite spheres freely moving in the dense bed of a lab-scale fluidized bed facility. It is shown that the heat transfer coefficient first increases as the fluidizing velocity rises initially from the minimum fluidizing velocity. After the fluidizing velocity reaching a critical point, the heat transfer coefficient remains invariant as the fluidizing velocity increases, which indicates that the burning coal particles remain in the emulsion phase in a CFB boiler. Under most conditions, the heat transfer coefficient decreases with the increase of bed material size, but at relatively low fluidizing velocities, after reaching a minimum value, the heat transfer coefficient increases with the bed material size. With fixed fluidizing velocity and bed material size, as the graphite diameter increases, the heat transfer coefficient declines and the dropping rate decreases. The heat transfer coefficient is higher for the graphite sphere floating in a higher bed.
    Hot-state experiment on double-pipe heat exchanger under coupled effect of fouling and acid
    LI Fei, SUN Fengzhong, SHI Yuetao
    2014, 65(8):  2876-2881.  doi:10.3969/j.issn.0438-1157.2014.08.003
    Abstract ( 536 )   PDF (2181KB) ( 391 )  
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    Flue gas dew point is the key indicator of low temperature corrosion, and restricts deep utilization of boiler flue gas heat. Fouling of heat exchanger surface is a major factor in deterioration of heat transfer. When fluid flows across heat exchange tubes, fouling and acid condensation influence heat transfer of heat exchanger. In the flue gas environment with dust and acid, a hot-state test was conducted to analyze heat transfer characteristics at different outer wall temperatures, and the dew point of flue gas for engineering application was obtained with a higher use value. The influence of the tubes' heat transfer characteristics with varying fouling and acid condensation was determined. Ash deposition with different amounts of acid condensation was investigated through analyzing the ash samples at different outer wall temperatures. The value of applied dew point for engineering was given as 72℃, which was at least 35℃ lower than the acid dew point in thermodynamics.
    Lattice Boltzmann simulation of droplet breakup dynamic behavior under electric field
    LI Chao, WU Huiying, HUANG Rongzong
    2014, 65(8):  2882-2888.  doi:10.3969/j.issn.0438-1157.2014.08.004
    Abstract ( 1153 )   PDF (1294KB) ( 460 )  
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    The pseudo-potential model of the lattice Boltzmann method (LBM) coupled with the discrete electric field governing equations was used to simulate the dielectric-medium droplet breakup process under electric field. By introducing deformation rate as a measurement of droplet's deformation, the whole evolution process of the droplet from deformation to breakup was presented. The influences of applied electric field strength and dielectric permittivity ratio of component inside to outside the droplet on the dynamic behavior of droplet breakup were investigated. Applied electric field promoted the deformation of droplet with deformation rate oscillating with time. There existed a critical electric capillary number (i.e. critical electric field strength) or a critical dielectric permittivity ratio, above which deformation rate oscillation amplitude was magnified continuously until breakup happened and below which the oscillation amplitude of deformation rate decayed continuously until deformation rate stabilized to a final steady value. Based on the simulation results, a modification of the present definition of electric capillary number was presented. With the modified electric capillary number, the influences of both electric field strength and dielectric permittivity ratio on droplet deformation and breakup could be analyzed integrally using a single parameter.
    Heat and mass transfer in osmotic distillation
    WANG Pan, ZHAO Jie, CHEN Huayan, LÜ Xiaolong
    2014, 65(8):  2889-2895.  doi:10.3969/j.issn.0438-1157.2014.08.005
    Abstract ( 607 )   PDF (472KB) ( 352 )  
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    Considering that the temperatures between the both sides of the membrane are quite close or even the same in osmotic distillation system, there is no phase inversion heat loss in this process. It is possible to achieve a lower energy consumption of membrane distillation process. Therefore, the study on seawater desalination by osmotic distillation was carried out. Firstly, the osmotic distillation experiments were proceeded with the seawater as feed solution, the glucose solution and calcium chloride solution as extractant in seawater desalination. The result showed that the membrane flux of calcium chloride solution as extractant was higher than that of glucose solution. Then the heat and mass transfer model of osmotic distillation was founded, based on which the calculation was carried out. The result showed that the model predictions were in good agreement with the experimental data. Thirdly, The impact of glucose solution or calcium chloride solution as extractant to mass transfer coefficient and polarization phenomenon was calculated. The result revealed that the mass transfer coefficient of calcium chloride solution as extractant is 1.7 times of glucose solution and the reduced value of the steam pressure difference by polarization phenomenon is a quarter of that for the latter.
    Mathematical modeling for height of absorption region in spray tower for limestone-gypsum wet flue gas desulfurization
    ZHU Jie, YE Shichao, WU Zhenyuan, BAI Jie, ZHENG Yijun
    2014, 65(8):  2896-2901.  doi:10.3969/j.issn.0438-1157.2014.08.006
    Abstract ( 727 )   PDF (504KB) ( 481 )  
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    Specific surface area and mass transfer rate in spray tower were studied by considering the forces acting on a droplet. Absorption region was divided into accelerating segment and constant speed segment, and a segmentation calculation model for the height of absorption region was developed, which was verified by the data of four industrial desulfurization systems. The effects of operating parameters on the height of absorption region were investigated. The results show that height of absorption region decreases with the decrease of spray density and pH value of absorbent, and increases with the decrease of droplet diameter, superficial gas velocity and inlet SO2 concentration. The desulfurization efficiency increases with the height of absorption region. When the desulfurization efficiency reaches above 90%, the height of absorption region only has a slightly influence on the efficiency.
    Condensation and collapse of bubbles in region of microbubble emission boiling
    TANG Jiguo, YAN Changqi, SUN Licheng, ZHU Guangyu
    2014, 65(8):  2902-2907.  doi:10.3969/j.issn.0438-1157.2014.08.007
    Abstract ( 680 )   PDF (1313KB) ( 491 )  
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    To illustrate the bubble dynamics in microbubble emission boiling (MEB), a high-speed video camera (Fastcam SA5) was employed to observe the boiling phenomena on a heating surface with a diameter of 10 mm at the liquid subcooling of 15-60 K. An equivalent radius was induced to analyze the bubble behavior in different boiling regions. It is showed that the bubble behavior of MEB differs from that of nucleate boiling and film boiling obviously. In the regime of MEB, a large irregular bubble commonly forms on the heating surface and collapses immediately, but not departures from the heating surface. The period of bubble ebullition is shorter, with a faster change rate in volume. A dimensionless analysis shows that the inertia control increasingly dominates the process of bubble collapse with the increase of wall superheat and heat flux.
    A preliminary experimental study on start-up behavior in nitrated gravity heat pipe
    MENG Qiang, WU Yuting, XIONG Yaxuan, CUI Wujun, LIU Shanwei, MA Chongfang, LI Deying
    2014, 65(8):  2908-2913.  doi:10.3969/j.issn.0438-1157.2014.08.008
    Abstract ( 562 )   PDF (524KB) ( 283 )  
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    Molten salt is a highly efficient heat transfer working fluid. It is widely used in central solar power, nuclear reactor, and heat treatment of metals. The startup process of gravity heat pipe with mixed nitrate as the working fluid was investigated experimentally by analyzing the startup characteristics, stability, and the influence of inclination angle on the startup behavior. The gravity heat pipe was fabricated with 316 L stainless steel, with outer diameter of 22 mm, thickness of 2 mm and total length of 980 mm. In order to explore the heat pipe start-up behavior of mixed nitrates, the experimental result with 40 g mixed nitrate working fluid is compared to that with 40 g naphthalene working fluid. The startup time of heat pipe with mixed nitrates is shorter than that with naphthalene and the heat pipe with mixed nitrates is superior to that with naphthalene in the stability. The boiling point of mixed nitrate is about 250℃. The startup characteristics at inclination angle of 50° are superior to those at 30°, 70° and 90°. The experiment shows that it is feasible for using mixed nitrates as the working fluid of heat pipe.
    Jet flow pattern and its effects on mass transfer area and gas phase pressure drop in a water-sparged aerocyclone
    CHENG Zhiliang, QUAN Xuejun, YAN Yunpeng, DAI Li
    2014, 65(8):  2914-2920.  doi:10.3969/j.issn.0438-1157.2014.08.009
    Abstract ( 569 )   PDF (3177KB) ( 247 )  
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    Water-sparged aerocyclone (WSA) is high efficiency gas-liquid mass transfer equipment, which takes the advantage of coupling effect of gas cyclone and liquid jet fields.In order to investigate the mechanism of jet-cyclone system of WSA and improve its mass transfer performance, jet flow pattern and its transformation was investigated by direct observation. Effective gas-liquid interfacial area per unit volume (a) of the WSA was also determined by chemical reaction method with CO2-NaOH solution system. The results show that jet flow pattern is mainly affected by jet velocity and air inlet velocity. There exists five jet flow patterns in the WSA, i.e., steady state jet, deformed spiral jet, broken spiral jet, atomized spiral jet and total atomized spiral jet at jet velocity less than 4.42 m·s-1. At the jet velocity higher than 6.19 m·s-1 there exists only three jet flow patterns, i.e. deformed spiral jet, broken spiral jet and atomized spiral jet. The value of a is related to jet flow pattern, higher in atomized spiral jet than in other jets, and increases with liquid jet velocity because of the intense gas-liquid interaction in the WSA.
    A new model for calculating effective thermal conductivity of metal foam
    YAO Yuanpeng, LIU Zhenyu, WU Huiying
    2014, 65(8):  2921-2926.  doi:10.3969/j.issn.0438-1157.2014.08.010
    Abstract ( 818 )   PDF (1229KB) ( 676 )  
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    A new model for calculating effective thermal conductivities of different metal foams is proposed based on an appropriate geometrical modeling method. The geometrical modeling is based on the representative cell geometry of metal foam, Kelvin tetrakaidecahedron, and the foam ligament is geometrically represented by concave tri-prism. The characteristic of foam node is also taken into account in the model. A general expression for calculating effective thermal conductivity is derived from thermal resistance analysis. In the present model, no geometrical parameter needs to be determined through experiments to describe the relationship between foam ligament and node. Compared with available experimental data and semi-empirical models in literature, the present model can accurately predict the effective thermal conductivities of different metal foams saturated with different mediums, with the average relative deviations from the experimental data within 10%. Considering both accuracy and generality, the present model is superior to existing semi-empirical models.
    Numerical simulation of cold state liquid flow in scrubbing-cooling ring
    YAN Liucheng, WAN Yifei, WANG Lingping, PAN Fei, GUO Qiangqiang, YU Guangsuo
    2014, 65(8):  2927-2933.  doi:10.3969/j.issn.0438-1157.2014.08.011
    Abstract ( 332 )   PDF (2731KB) ( 318 )  
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    In order to investigate the flow behavior of cooling water in scrubbing-cooling ring, especially at the outlet of the ring, a mathematical model for the fluid flow in scrubbing-cooling ring was established with Fluent, a software of computational fluid dynamics. The experimental study was carried out to measure the average velocity at the outlet of scrubbing-cooling ring to verify the mathematical model. The velocity of jet hole and slot was obtained from experiment and simulation. The numerical simulation result fits the experimental result well. It suggests that vortex exists inside the scrubbing-cooling ring because of the structure of the ring. The motion of vortex is most violent along the circumference of inlet in the inner chamber, so that the average outlet velocity of jet hole at the circumference of inlet is the minimum and the velocity at the circumferential position between two inlets is the maximum. The distribution of average outlet velocity of slot at circumferential position is the same with that of jet hole.
    Visual experimental study on operation characteristics of condensation segment of gravity-assisted heat pipe
    HAN Zhenxing, WANG Dongxiao, WANG Fei, MA Shanchuan, WANG Yuwei, LIN Yanchao, LIU Shi
    2014, 65(8):  2934-2939.  doi:10.3969/j.issn.0438-1157.2014.08.012
    Abstract ( 628 )   PDF (5368KB) ( 538 )  
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    Visual experimental studies were conducted on the condensation process of a gravity-assisted heat pipe with electrical capacitance tomography (ECT) technology. The heat pipe was made of silica glass, and alcohol was used as working fluid. The heating temperature of its evaporation segment was controlled by a heater with different power outputs. The alcohol vapor in the condensation segment was cooled to condense through heat convection with cooling water. The condensation process of alcohol vapor was monitored by an ECT measurement system to observe the distribution characteristics of liquid and its vapor, and the formation and development of liquid film on the wall of the heat pipe. Considering the access limitations of the structure of the condensation segment, the traditional structure of the ECT transducer was changed. The shielding case was abandoned, and the measuring electrodes were sealed with insulating hydrophobic layer. This method made it possible to permit the transducer to be used in a liquid environment, and effectively expand the application fields of ECT technology. Alcohol vapor condensed in strips and unevenly on the wall surface when heating temperature of the evaporation segment was low. With increasing heating temperature, the condensing liquid would change to annular flow around the whole circumference. When heating temperature exceeded a specified limit, a kind of cyclical phenomenon happened. The liquid film gradually became thicker and even occupied the whole cross section of the heat pipe, and then fell off. This phenomenon occurred repeatedly, and its frequency increased with increasing heating temperature. When the gravity heat pipe was inclined 30° from the vertical direction, the same phenomenon appeared when heating temperature was 110℃.
    Heat transfer performance of pulsating heat pipes with water-acetone mixtures
    ZHU Yue, CUI Xiaoyu, HAN Hua, SUN Shende, LI Zhihua
    2014, 65(8):  2940-2947.  doi:10.3969/j.issn.0438-1157.2014.08.013
    Abstract ( 373 )   PDF (1664KB) ( 383 )  
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    Experiments of pulsating heat pipes (PHP) were conducted, with water, acetone and water/acetone binary mixtures at different ratios (13:1, 4:1, 1:1, 1:4, 1:13) under various filling ratios (35%-70%) and heat inputs (10-100 W). The experimental results were analyzed with the feature of physical property and phase change for mixture. The results show that because of lower boiling point, specific heat and latent heat for evaporation, the mixture solution requires lower heating power to initial PHP than water. At low filling ratios, compared to mixtures except that with relatively low acetone concentration (e.g. water/acetone 13:1), pure working fluids are relatively easier to dry out in PHP. With the heat input of 50 W, PHPs with pure working fluid are dried, while those with mixtures maintain relatively low thermal resistance. The mixture with a little water (e.g. water/acetone 1:13) can significantly improve the dry state in PHP, while that with a little acetone (e.g. water/acetone 13:1) does not significantly improve the dry situation. At high filling ratios, heat transfer performance of PHP with pure working fluids are better than mixtures. In the range from 35 W to 50 W, the PHPs with pure working fluids present lower thermal resistance. At higher heat input (50-100 W), the PHP with water has lower thermal resistance compared to that with mixture. The study on heat transfer performance of PHP provides references for further research on the heat transfer mechanism of PHP and establishment of theoretical models on heat transfer characteristics.
    Prediction of entrainment fraction at onset of annular flow based on 2006 CHF look-up table
    JIAO Bo, YANG Dongyu
    2014, 65(8):  2948-2953.  doi:10.3969/j.issn.0438-1157.2014.08.014
    Abstract ( 496 )   PDF (439KB) ( 218 )  
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    The critical heat flux (CHF) of gas-liquid flow plays an important role in the safety of industrial equipment. At present, the liquid film model is widely used for predicting critical heat flux in gas-liquid annular flow. It consists of onset of annular flow, entrainment fraction for the onset point and the equilibrium state, inception criteria for droplet entrainment, droplet deposition and entrainment rates, which all have decisive effect on prediction accuracy. Most parameters in this model can be determined by some empirical correlations valid under different conditions. However, up to now, the entrainment fraction for the onset of annular flow is always assumed. In this paper, the normalized data of the 2006 CHF look-up table adopted widely, especially in the nuclear industry, were used. The liquid film model was built for the limiting quality region. The entrainment fraction at the onset of annular flow was obtained when the predicted CHF of the model met the values in the look-up table. The empirical correlation including the Weber number and the Reynolds number of liquid was provided. Its prediction could mostly make the errors within ±30%.
    Single phase convective heat transfer enhanced by inserted mesh cylinder
    XING Feng, XIE Jian, XU Jinliang
    2014, 65(8):  2954-2962.  doi:10.3969/j.issn.0438-1157.2014.08.015
    Abstract ( 372 )   PDF (1228KB) ( 386 )  
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    A method was proposed to enhance the single phase convective heat transfer. A stainless mesh cylinder was inserted into the tube concentrically to divide its cross section into an annular region and a central region. As the fluid passes the mesh cylinder, most of it enters the annular region because of resistance, modulating the flow field. Hot fluid in the annular region and cold fluid in the central region mix with each other more intensely through the mesh surface, enhancing the heat transfer. The heat transfer and pressure drop characteristics in the vertical upward flow with inserted mesh cylinder were investigated experimentally to validate the method. The mean and local Nusselt numbers and pressure drop data were obtained from the mesh cylinder tube and a smooth tube with water as the working fluid. The Reynolds numbers cover the range of 2392-20175 and the heat flux is in the range of 50.18-282.88 kW·m-2. The experimental results from the smooth tube are validated by using the well known equations in literature. Inserting a mesh cylinder increases the heat transfer and pressure drop considerably compared with the smooth tube. The heat transfer enhancement factors range from 1.21 to 1.84. In the entrance region or thermal developing region, the heat transfer enhancement factor is up to 2.64. Meanwhile, the pressure drop is 6.1-10.6 times larger than that of the smooth tube.
    Improvement of structure design on swirl meter based on CFD
    CUI Baoling, CHEN Kun, ZHU Linhang, CHEN Desheng, HUANG Dunhui
    2014, 65(8):  2963-2969.  doi:10.3969/j.issn.0438-1157.2014.08.016
    Abstract ( 28 )   PDF (6845KB) ( 252 )  
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    In order to reduce the pressure loss of 150-caliber swirl meter, two programs of increasing the lead of swirler and the throat diameter of casing were adopted to improve the performance of swirl meter. In the flow range from 120 m3·h-1 to 2100 m3·h-1, numerical simulation and experiment were conducted to study the pressure loss characteristics and meter factor of the swirl meter before and after improvement, and internal flow characteristics of the section where piezoelectric sensors were located was analyzed. Through numerical simulation it was found that these two programs could reduce the pressure loss of swirl meter, but meter factor decreased with degraded precision. Small flow measurement could not be applicable because of the decrease of meter factor. If only considering the factor of pressure loss, program B (increasing the lead and the throat diameter) was better than the program A (only increasing the lead). The experiments were performed on sonic nozzle device to verify simulation results of two programs. The experimental results of pressure loss and meter factor basically agreed with numerical simulation results.
    Shell side fluid flow characteristics in helical baffled heat exchanger
    DU Wenjing, WANG Hongfu, CHENG Lin
    2014, 65(8):  2970-2975.  doi:10.3969/j.issn.0438-1157.2014.08.017
    Abstract ( 506 )   PDF (1073KB) ( 391 )  
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    Experimental study was explored with the ultrasonic Doppler velocimeter on the shell side fluid flow characteristics in helical baffled heat exchanger made from acrylic glass. Emphasis was on the axial velocity distribution characteristics. Results indicate that the axial velocity is uniformly distributed in the circumferential region of the shell side. Benefiting from the leakage flow in the triangular region, the corresponding axial velocity in the central region is rapidly increased. With the increase of mass flow rate, the variation magnitude of axial velocity in the central region is much larger than that in the circumferential region. An obvious fluctuation of axial velocity on the shell side of the helical baffled heat exchanger is also an important phenomenon. The mean velocity in the central region increases with the mass flow rate, but this feature is absent when the corresponding turbulent flow is dominant and backmixing flow occurs.
    Micromixing in rotating packed bed with ceramic foam packing
    ZHANG Wenjie, CHU Guangwen, LUO Yong, XIANG Yang, ZOU Haikui, CHEN Jianfeng
    2014, 65(8):  2976-2980.  doi:10.3969/j.issn.0438-1157.2014.08.018
    Abstract ( 490 )   PDF (973KB) ( 312 )  
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    Two kinds of ceramic foam packing with different apertures were used in a rotating packed bed (RPB). Micromixing efficiency in the RPB was experimentally studied by a parallel competing iodide-iodate reaction system, and segregation index (XS) was used to represent the efficiency. Effects of volumetric flow rate, concentration of H+, rotational speed, and volumetric flow ratio on the micromixing efficiency were investigated. Experimental results show that the ceramic foam packing with smaller aperture is better for micromixing. As concentration of H+ and volumetric flow ratio increase, XS increases, while it decreases with the increase of rotational speed and fluid flow rate. The micromixing time tm is calculated using incorporation model based on experimental results and the range of tm of ceramic foam packing is from 0.385 ms to 8.55 ms. Compared with traditional stainless steel mesh packing, the minimum value of tm of ceramic foam packing (0.385 ms) is much less than that of stainless steel mesh packing (1.6 ms). It means that ceramic foam packing presents better micromixing performance.
    Bubble behavior in sea water bubbling concentration process
    TAO Hengcong, ZHU Baikang, WANG Dongguang
    2014, 65(8):  2981-2987.  doi:10.3969/j.issn.0438-1157.2014.08.019
    Abstract ( 569 )   PDF (7497KB) ( 365 )  
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    Evaporation process for concentrating sea water can be enhanced by bubbling operation, and it is not only significantly influenced by bubble size but also movement of bubbles. Thus, two different sizes of bubbling test rigs were set up indoor and outdoor. The movement, distribution, coalescence and rupture of large bubbles and small bubbles were experimentally analyzed with a single aeration inlet, two aerations inlets and multi-inlets at different gas fluxes, depths and inlet spacings. Small bubbles floating on the liquid surface had higher coverage and scattered more smaller droplets than large bubbles at a lower gas flow flux, implying that the small bubble pattern was more efficient in bubbling for the solar sea water concentration process. The coverage rate of small bubbles in the operation could reach 90%, increasing evaporation rate by 1-1.5 times, based on optimized operational parameters with gas flux at 0.4 L · min-1, level depth at 8 cm and inlet spacing at 12 cm.
    Catalyst for one-step production of synthetic natural gas from coal
    BAI Shaofeng, GUO Qingjie, XU Xiufeng
    2014, 65(8):  2988-2996.  doi:10.3969/j.issn.0438-1157.2014.08.020
    Abstract ( 774 )   PDF (2623KB) ( 603 )  
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    An investigation into catalyst was conducted for one-step production of synthetic natural gas from coal in a fixed bed reactor using steam as gasification medium. The reactivity and stability of K-Fe catalyst in multi-cycles, as well as the kinetics model of methanation process and the effect of different coals on methanation, were studied. K15Fe10Ca5 catalyst showed significantly better activity in the coal gasification and methanation reactions at 650℃ and 2 MPa. Furthermore, X-ray diffraction data indicated that some highly active materials, such as K6Fe2O5 were formed by interaction of active components and enhanced reactivity. With the addition of calcium promoter, combination of active components and minerals in coal was prevented and the sulfur in coal could be fixed effectively. In multi-cycle experiments, CH4 yield remained stable. The methanation mechanism of Shenmu-coal with K15Fe10Ca5 could be described by the modified random pore model proposed, suggesting that interfacial reaction was the control step. The final yield was affected by volatile matter, ash content, and sulfur content.
    Catalytic performance of Ni-Mn/Al2O3 catalyst for CO methanation in slurry-bed reactor
    MENG Fanhui, CHANG Huirong, LI Zhong
    2014, 65(8):  2997-3003.  doi:10.3969/j.issn.0438-1157.2014.08.021
    Abstract ( 12 )   PDF (4672KB) ( 459 )  
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    Ni-Mn/Al2O3 catalysts with different contents of Mn were prepared by co-impregnation method, and the catalytic performance for CO methanation in slurry-bed reactor was studied. The catalysts were characterized by XRD, H2-TPR, BET, TEM and H2-chemisorption. The addition of Mn promoted the dispersion of Ni species, weakened the interaction between Ni species and support, decreased the reduction temperature, increased the catalyst specific surface area and decreased the particle size of active metallic Ni. With the increase of Mn content, the catalytic performance of Ni-Mn/Al2O3 catalysts increased firstly and then decreased, and the catalyst Ni-Mn/Al2O3 with Mn content of 4% exhibited the best catalytic performance. Excess addition of Mn decreased catalytic performance, because the active component Ni was covered by Mn. The investigation on effects of reaction temperature and reaction pressure showed that under the reaction conditions of 280℃ and 1.5 MPa, conversion of CO and selectivity of CH4 for the catalyst sample 16Ni4Mn/Al2O3 reached 96.2% and 88.8%, respectively.
    Catalytic hydrodeoxygenation of fast pyrolysis bio-oil of chlorella over Ni-Cu/ZrO2 catalyst
    ZHANG Liang, WU Man, YANG Ya, ZHANG Xiuli, XU Xiufeng, GUO Qingjie
    2014, 65(8):  3004-3011.  doi:10.3969/j.issn.0438-1157.2014.08.022
    Abstract ( 14 )   PDF (945KB) ( 231 )  
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    The catalytic hydrodeoxygenation of bio-oil obtained by fast pyrolysis of chlorella over Ni-Cu/ZrO2 catalyst was carried out in a fixed-bed reactor to improve the quality of the bio-oil. The catalysts were characterized by XRD, H2-TPR, TG and NH3-TPD techniques. The results showed that the addition of Cu promoted dispersion of active species, and increased catalytic hydrodeoxygenation activity of Ni-Cu/ZrO2 catalysts. However, the activity went up first, and then went down with increase of Cu loading. A possible theoretical explanation was also given. At reaction conditions of 2 MPa and 350℃, the performance of Ni-Cu/ZrO2 catalyst was stable and it made the oxygen content in the bio-oil decreased sharply. For the Ni-Cu/ZrO2 catalyst with Cu/Ni mass ratio of 0.40, the efficiency of oxygen removal was 82.0% after 3 h reaction and larger than 77.0% after 24 h reaction. The heat value of upgraded bio-oil increased from 31.5 MJ·kg-1 to 35.0 MJ·kg-1, while the kinetic viscosity at 40℃ fell from 20.5 mm2·s-1 to 9.5 mm2·s-1 after hydrodeoxygenation reaction. In addition, the water in upgraded bio-oil could be removed easily. Furthermore, the stability of upgraded bio-oil was improved significantly due to the reduction of unstable acids.
    Catalytic performance of metal phthalocyanine loaded on MCM-41 molecular sieve in oxidation desulfurization
    ZHANG Juan, REN Tengjie, HU Yanhui, LI Junpan, WANG Chunfang, ZHAO Dishun
    2014, 65(8):  3012-3018.  doi:10.3969/j.issn.0438-1157.2014.08.023
    Abstract ( 40 )   PDF (532KB) ( 312 )  
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    Eight kinds of metal phthalocyanine (Pc) were loaded into MCM-41 by impregnation method,and were characterized by infrared spectrum. The catalytic activities of the eight supported metal phthalocyanine in the desulfurization were investigated with dibenzothiophene (DBT) as the reaction substrate, air as oxidant and caprolactam-tetrabutylammonium bromide ionic liquid as solvent. The reaction condition was investigated in detail. The results showed that MCM-41/CoPc was the best catalyst among the eight supported metal phthalocyanine catalysts. The removal ratio of DBT is up to 97.56% for 1 h under the optimal reaction condition (the ratio of ionic liquid to model oil 1:1, the amount of catalyst 0.004 g·(10 ml model oil)-1, air flow rate 50 ml·min-1 and room temperature). The oxidized product of DBT is DBT sulphone. Different sulfur compounds were also investigated. The result shows that sulfur removal of different sulfur all are up to 90%. The removal ratio of DBT doesn't decrease obviously, after reused for four times with this catalyst.
    Preparation and gas separation performance of hydrophobic SiO2/PTFPMS hybrid composite membrane
    NIE Fei, HE Gaohong, ZHAO Wei, JU Jia, LI Hao
    2014, 65(8):  3019-3025.  doi:10.3969/j.issn.0438-1157.2014.08.024
    Abstract ( 697 )   PDF (4881KB) ( 448 )  
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    To improve the solvent resistance property of gas separation membrane, a hydrophobic SiO2/polytrifluoropropylsiloxane (PTFPMS) hybrid composite membrane was fabricated on a porous polyetherimide (PEI) support with solution blending method. The effects of mass ratio of hydrophobic SiO2 to PTFPMS on the membrane morphology, solvent resistance, and gas separation performance of the hydrophobic SiO2/PTFPMS hybrid composite membrane were investigated. The optical microscope images show good miscibility between SiO2 and PTFPMS with the increase of blend ratio till 0.018. At blend ratios higher than 0.018, SiO2 particles exhibit obvious aggregation in the hybrid membrane. SEM images show that no obvious defect is on the surface of the SiO2/PTFPMS selective layer that is closely stuck on the PEI support. The swelling degree of the hydrophobic SiO2/PTFPMS hybrid homogeneous film is 0 in nonpolar solvent octane and is declined by 11.9% in polar solvent ethyl acetate compared with PTFPMS homogeneous film, indicating the improved solvent resistance of the SiO2/PTFPMS hybrid homogeneous film. The CO2 gas permeation rate can reach as high as 156.1 GPU and the selectivity of CO2/N2 is 15.86 when the blend ratio of SiO2 is 0.012 under the transmembrane pressure difference up to 1.0 MPa.
    Molecular permeation in nanoporous graphene gas separation membranes
    SUN Chengzhen, ZHANG Feng, LIU Hai, BAI Bofeng
    2014, 65(8):  3026-3031.  doi:10.3969/j.issn.0438-1157.2014.08.025
    Abstract ( 537 )   PDF (1702KB) ( 586 )  
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    A molecular dynamics simulation was performed to probe the mechanism of molecular permeation through nanoporous graphene gas separation membranes. The investigation involves 4 different gas molecules (He, H2, N2 and CH4) permeating 9 graphene nanopores with different sizes. The results show that the permeation flux depends not only on the kinetic parameters of molecules, i.e. molecular mass and kinetic diameter, but also on the adsorption of molecules on the surface of graphene membrane. Apart from the permeation free of interactions with the graphene surface, the adsorption layer composed of molecules with high densities on the graphene surface provides an additional way for molecular permeation, increasing the permeation flux as the molecular adsorption increases. In addition, the permeation flux of H2 molecules increases linearly with the pressure for different graphene nanopores.
    Adsorption of glycine on resin D301
    LI Wenli, ZHOU Cairong
    2014, 65(8):  3032-3038.  doi:10.3969/j.issn.0438-1157.2014.08.026
    Abstract ( 912 )   PDF (532KB) ( 399 )  
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    The adsorption of glycine on resin D301 in glycine aqueous solution was investigated by static adsorption experiments. The optimum adsorption conditions were found by single factor experiments: adsorbent dosage 0.1 g, pH value of solution 7.5, and temperature 35℃. Under these adsorption conditions, the time required for adsorption equilibrium was 45 min, with the maximal equilibrium adsorption amount as 794.81 mg·g-1. The thermodynamic performance of the adsorption process was investigated in the range from 303.15 K to 318.15 K. Langmuir, Freundlich and Temkin isothermal adsorption models were employed to fit the experimental data. The results show that the adsorption of glycine on resin D301 is in accordance with the Langmuir isothermal adsorption model. The thermodynamic parameters, such as ΔHθ, ΔGθ, ΔSθ and apparent activation energy, were calculated to be 134.75 kJ·mol-1,-6.312 kJ·mol-1, 450.806 J·mol-1·K-1, and 81.27 kJ·mol-1, respectively. The results indicate that the adsorption process of glycine onto resin D301 is a spontaneous endothermic process with physical and chemical adsorption.
    Preparation and adsorption behavior of Cu(Ⅱ) ion-imprinted composite membranes via electrostatic assembly
    FAN Rongyu, ZHENG Ximing, LIN Xing
    2014, 65(8):  3039-3047.  doi:10.3969/j.issn.0438-1157.2014.08.027
    Abstract ( 492 )   PDF (4597KB) ( 391 )  
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    The layer-by-layer electrostatic assembly process and chemical cross-linking technology were developed for Cu(Ⅱ) ion-imprinted composite membranes. Poly(acrylic acid) and polyethylenimine-copper(Ⅱ) ion complexes were assembled alternately on the surface of microporous polypropylene membrane (MPPM) by electrostatic action. Then the assembled layers were cross-linked by epichlorohydrin. The Cu(Ⅱ)-ion imprinted composite membranes obtained after the removal of Cu(Ⅱ) ions with acetic acid, characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and environmental scanning electron microscopy, show satisfactory hydrophilicity and stability. The composite membrane can take water up to 819 times that of MPPM. The mass of assembled layers can maintain more than 94% after oscillating washing in 1.5 mol·L-1 NaCl solution or in 55℃ water for 48 h. The equilibrium adsorption experiments indicate that the ion-imprinted composite membranes exhibit high adsorption capability and high selectivity towards Cu(Ⅱ). The maximum adsorption capacity is 112.87 mg·cm-2, and the selectivity coefficients are 17.72, 26.66, 17.43, 16.87, 29.72 and 19.75 with Pb(Ⅱ), Zn(Ⅱ), Ni(Ⅱ), Co(Ⅱ), Mg(Ⅱ) and Mn(Ⅱ) as competing ions, respectively. The adsorption thermodynamics and kinetics show that the adsorption process of Cu(Ⅱ) is in monolayer adsorption and is dominated by chemical interaction. The ion-imprinted composite membranes exhibit good regeneration ability, and their adsorption capacity can be maintained over 90% even after ten adsorption-desorption cycles.
    Salting-out extraction of phenolics from grape (Vitis vinifera) seed
    DANG Yanyan, GUO Yuxi, CAO Wenjing, XIU Zhilong
    2014, 65(8):  3048-3053.  doi:10.3969/j.issn.0438-1157.2014.08.028
    Abstract ( 460 )   PDF (861KB) ( 289 )  
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    Salting-out extraction system composed of ethanol and ammonium sulfate was used to separate total phenolics, flavonoid, and proanthocyanidin from wine grape seed. The experimental results showed that components were extracted into the top ethanol-rich phase (the system consisted of 30% (mass) ethanol/18% (mass) ammonium sulfate) to give the yield of total phenolics, flavonoid, and proanthocyanidin in 64.54, 42.45, and 23.16 mg·g-1, and corresponding recovery rates in 97.31%, 98.19%, and 97.92%, respectively. The antioxidant activity of seed extracts were assayed with radical-scavenging ability (IC50) of 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) at room temperature. The seed extracts by salting-out extraction showed lower IC50 (61.85 and 71.76 mg·L-1) than that by heat reflux extraction (78.73 and 90.34 mg·L-1).
    Enhancement factor of CO2 absorption by ethanolamine aqueous solution in packed tower
    LIU Yingshu, WEI Guangfei, ZHANG Hui, LI Hu, LI Xiaokang
    2014, 65(8):  3054-3061.  doi:10.3969/j.issn.0438-1157.2014.08.029
    Abstract ( 618 )   PDF (569KB) ( 679 )  
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    CO2 absorption by aqueous alkanolamine solution is an important research topic in the field of biogas purification. A packed tower was used to investigate the CO2 absorption by ethanolamine (MEA) solutions. The effective gas-liquid interfacial area was calculated from the experimental results of CO2 absorption by sodium hydroxide aqueous solutions. A mathematical model was proposed to calculate the enhancement factor of the CO2 absorption of relatively high concentration by MEA aqueous solutions. The influence of various technological parameters on the enhancement factor of CO2 absorption by MEA was analyzed from the two aspects of mathematical model and experiment, including gas flow rate, MEA concentration and CO2 concentration. The results show that the model predictions are in good agreement with the experimental values. The enhancement factor of CO2 absorption by MEA increases with the increment of MEA concentration and decreases with the increment of CO2 concentration and gas flow rate.
    Dynamic process based soft sensing of melt flow rate
    WEI Yujie, SHANG Chao, GAO Xinqing, FAN Zhi, HUANG Dexian
    2014, 65(8):  3062-3070.  doi:10.3969/j.issn.0438-1157.2014.08.030
    Abstract ( 369 )   PDF (952KB) ( 317 )  
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    Grade transition processes are critical for saving energy in polymerization, however, the traditional models do not pay much attention to the transitional process due to insufficiency of quality data. Therefore, based on the previous work of the three-stage decomposition modeling method, the overall process is further dealt with. In the polypropylene process, there are stable production processes for a single grade and grade transitional processes between two different grades. As these two kinds of processes have different dynamic characteristics, it is reasonable to divide data into different sub-domains according to different dynamic processes and develop sub-models in every domain. In this paper, construct ensemble of models based on different dynamic processes and a discriminant model to detect the beginning and completion of the transition were proposed. Finally, the proposed model was applied to industrial plant data and its higher prediction performance was verified, compared with a single model.
    Multimode process monitoring based on local density estimation
    LIU Bangli, MA Yuxin, SHI Hongbo
    2014, 65(8):  3071-3081.  doi:10.3969/j.issn.0438-1157.2014.08.031
    Abstract ( 507 )   PDF (757KB) ( 523 )  
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    Multiple operating modes and complex data distributions are common in modern industrial processes, so the process variable does not completely obey Gaussian distribution, and its mean and covariance structure tend to change with the switching of working conditions. In order to detect various faults in such production process timely, a novel online monitoring strategy based on locality preserving projection (LPP) and local density estimation with variable bandwidth is proposed. Firstly, LPP is introduced for feature extraction and dimension reduction, and then a variable bandwidth kernel density estimate function is adopted to compute every sample's local density factor, which is used as a monitoring statistic value. Finally, the results of numerical examples and TE chemical process simulation experiment validate the effectiveness and utility of the proposed method for the fault detection of multi-mode processes.
    Preparation and characterization of hollow fiber forward osmosis membrane by interfacial polymerization
    LI Gang, WANG Zhouwei, LI Chunxia, LI Xuemei, HE Tao, GAO Congjie
    2014, 65(8):  3082-3088.  doi:10.3969/j.issn.0438-1157.2014.08.032
    Abstract ( 455 )   PDF (1498KB) ( 371 )  
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    Hollow fiber thin film composite forward osmosis membrane was prepared on the top of a tailor-made polysulfone hollow fiber support by interfacial polymerization. The relationship between casting parameters, membrane structure, and FO performance was studied. The results showed that the thickness of substrate membrane was one of the main factors affecting FO performance. The thicker membrane could cause more serious internal concentration polarization, leading to lower effective osmotic pressure across the membrane as well as water flux in the FO process. A thin film composite membrane with a thickness of 0.129 mm and force at breakage of 2.48 N was obtained. The FO membrane showed a water flux of 10.3 L·m-2·h-1 and a specific salt diffusion of 0.15 g·L-1.
    Analysis of surface deformation and seal performance of mechanical face seal with diamond macro-pores
    CHENG Xiangping, MENG Xiangkai, PENG Xudong
    2014, 65(8):  3089-3097.  doi:10.3969/j.issn.0438-1157.2014.08.033
    Abstract ( 539 )   PDF (9910KB) ( 275 )  
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    For a liquid lubricated end face mechanical seal with diamond macro-pores, the finite difference method was used to solve the two-dimension Reynolds equation for the isothermal, laminar and incompressible lubrication film and film pressure distribution was obtained. Finite element software was used to calculate surface deformation of seal rings. Deformation and seal performance parameters, such as friction torque, liquid film stiffness and leakage rate were investigated under different operating conditions for different sealing rings constructions. The results showed that the end face of mechanical seal deformed with circumferential waviness and radial coning. Convergent and divergent deformations occurred according to different operating conditions, hence seal performance greatly changed. When B was 0.65-0.75, the mechanical seal could achieve better sealing performance. The location of the secondary O ring greatly influenced radial taper deformation, the range of l preferred values was 2.4-4.0 mm.
    Amperometric hydrogen permeation flux method for online corrosion monitoring of oil and gas pipelines
    LIU Xianglu, ZHANG Deping, DONG Zehua, LIU Fufa
    2014, 65(8):  3098-3106.  doi:10.3969/j.issn.0438-1157.2014.08.034
    Abstract ( 756 )   PDF (1413KB) ( 424 )  
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    The effects of pH, temperature and H2S concentration on hydrogen permeation current and corrosion rate of Q235A carbon steel in weakly acidic medium were studied with the potentiostatic anodic polarization and mass loss methods. The relationship between hydrogen permeation current density and corrosion rate was investigated, aiming at using the hydrogen flux method in online non-intrusive corrosion monitoring of oil pipelines. Increasing acidity and temperature could boost hydrogen permeation current and corrosion rate of Q235A steel in the corrosive solutions, with a good linear relationship between them. The corrosion rate of Q235A steel increased initially and then decreased slightly with increasing concentration of H2S. Meanwhile, hydrogen permeation current also increased at first and then stabilized. When the concentration of H2S was 5-200 mg·L-1, there was a quadratic function between corrosion rate and hydrogen permeation current. Based on inner corrosion monitoring of an experimental pipe by a self-made hydrogenermeation flux probe, the thick pipe wall could decrease the sensitivity of hydrogen permeation current. However, by the help of step potentiostatic polarization, hydrogen permeation flux was found to be linearly related to the corrosion rate of Q235A steel measured by mass loss, indicating that the hydrogen permeation flux could be applicable for the non-intrusive inner corrosion monitoring of thick oil pipelines.
    Preparation of cationic polyacrylamide microspheres by concentrated emulsion polymerization and its size evolution
    LI Guanghui, ZHANG Guicai, WANG Hao, GE Jijiang, LIU Yueliang
    2014, 65(8):  3107-3113.  doi:10.3969/j.issn.0438-1157.2014.08.035
    Abstract ( 506 )   PDF (2586KB) ( 296 )  
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    Concentrated emulsion polymerization has great potential use in oil production due to its product characteristics of high stability and proper particle size close to formation pore, which complements the gel particles synthesized by microemulsion polymerization and suspension polymerization. A series of concentrated emulsion were prepared based on microemulsion with acrylamide and methylacryloxylethyl trimethyl ammonium chloride as monomers. The structure, size distribution, stability of this emulsion before and after polymerization were determined by conductivity measurement, rheology analysis, and microscope observation. The results showed that both viscosity and yielding stress decreased with increasing monomer concentration (CM) in water phase and had a maximum value with increasing surfactant content (mS). The same trend was found for emulsion stability. The emulsion destability of CM >40% or mS =2.5 g was separately attributed to percolation effect and insufficiency emulsification in high dispersion viscosity; especially, the particle size with 1-30 mm and bimodal distribution before polymerization evolved to that with 0.4-5 mm and unimodal distribution after polymerization. This size evolution could be explained by Kolmogoro-Hinze emulsification theory, further testified by the phenomenon that the viscosity of microsphere emulsion was enhanced as much as ten times that of emulsion before polymerization.
    Electrochemical characterization of energy level of functionalized carbon microspheres
    YAN Lingpeng, HAO Yamin, YANG Weijia, YANG Yongzhen, LIU Xuguang, XU Bingshe
    2014, 65(8):  3114-3121.  doi:10.3969/j.issn.0438-1157.2014.08.036
    Abstract ( 470 )   PDF (4240KB) ( 410 )  
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    Two kinds of carbon microspheres (CMSs) were prepared by the hydrothermal method and chemical vapor deposition (CVD), the CMSs prepared by CVD (CCMSs) were oxidized by a mixture of concentrated sulfuric acid and nitric acid (volume ratio of 3:1) to improve their surface activity, while the CMSs prepared by the hydrothermal method (HCMSs) were used as obtained. Then, two kinds of CMSs reacted with1,6-hexanediamine to prepare aminated CMSs with N,N'-dicyclohexyl carbodiimide as condensation agent. The morphology and structure of products were characterized with field emission scanning electron microscopy and Fourier transform infrared spectrometry. The thermostability and energy level structure were characterized with thermogravimetry and electrochemical analysis, the optical properties were characterized with fluorescence analysis. Both CMSs met the requirement of energy level as receptor materials in polymer solar cell, and amination increased the LUMO energy level of CMSs. HCMSs was superior to CCMSs in morphology, dispersibility in solvents and thermal stability, so HCMSs could be more suitable for using as the receptor materials of polymer solar cell.
    Screening and cellulase production of recombinant Trichoderma reesei with high activity exo-β-glucanases
    KONG Qin, FANG Hao, XIA Liming
    2014, 65(8):  3122-3127.  doi:10.3969/j.issn.0438-1157.2014.08.037
    Abstract ( 428 )   PDF (816KB) ( 407 )  
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    Increasing the activities of exo-β-glucanases, one of the important components of cellulase, is a key to strengthening the synergistic degradation of cellulase and reducing the cost of cellulolytic hydrolysis. The methods of MCC-agar plate screening and liquid culture medium of filter paper were used in this work respectively to screen Trichodermareesei transformants, obtaining 6 superior transformants with higher filter paper collapsing rate and growing rate on MCC-agar plates. Further screening experiment was conducted under shaking flask condition, obtaining the highly exo-b-glucanase (C1)-producing transformant T.reesei ZU-101 whose C1 activity was18.24 U·ml-1 after 48 h liquid culture, 2.16-fold higher than the original strain. Analysis results demonstrated that filter paper activity (FPA) of the cellulase system of the transformant, representing total activity, increased by 61.9% as exo-β-glucanase activity ascended significantly, although endo-b-glucanase and cellobiase activities varied insignificantly from the original strain. The enzymatic hydrolysis yield of T.reesei ZU-101's cellulase in the hydrolysis of alkali pretreated corn stover was 94.4% when the enzyme dosage and hydrolysis time were 20 FPIU·(g substrate)-1 and 48 h, respectively. The results of the present work have promising application prospects in the bioconversion and utilization of renewable cellulosic materials.
    Construction of heat resistance devices for Escherichia coli and their application
    SUN Xiangying, LIU Yueqin, SUN Huan, JIA Haiyang, DAI Dazhang, LI Chun
    2014, 65(8):  3128-3135.  doi:10.3969/j.issn.0438-1157.2014.08.038
    Abstract ( 446 )   PDF (1784KB) ( 307 )  
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    To improve the heat resistance of Escherichia coli, an inducible heat-resistance device T7-T.te-HSP20 and a constitutive heat-resistance device gapA-T.te-HSP20 based on T.te-HSP20 gene from Thermoanaerobacter tengcongensis MB4, and corresponding engineered strains E. coli-TH and E. coli-GH were constructed. The targeted protein was expressed in solubility after IPTG induction at 30℃ in E. coli-TH. Meanwhile, the survival rate of E. coli-TH was 3.2 times higher than the control at 50℃ for 30 min. The result of high-temperature fermentation showed that the optimum temperature range of E. coli-GH was broadened (37-43℃) under the regulation of heat resistance device gapA-T.te-HSP20. Stress resistance analysis showed that E. coli-GH not only possessed heat resistance and butanol resistance, but also had some resistance to acetic acid and ethanol. These results provide a new idea for modern microorganisms industry.
    CO chemical looping combustion using Co-Fe2O3 nano oxygen carrier for enrichment of CO2
    QIN Wu, LI Qu, DONG Changqing, CHENG Weiliang, YANG Yongping
    2014, 65(8):  3136-3143.  doi:10.3969/j.issn.0438-1157.2014.08.039
    Abstract ( 481 )   PDF (1115KB) ( 306 )  
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    Co-doped Fe2O3 of different orders of magnitude were prepared as oxygen carriers, the structures of which were characterized with adsorption-desorption (BET) and transmission electron microscope (TEM). Experiments under different temperatures were performed to investigate the reaction between Co-doped Fe2O3 and CO to understand the chemical looping combustion characteristics of these prepared oxygen carriers. The higher the doping amount, the higher the reduction conversion at the same temperature. However, with the same doping amount, increase of temperature led to increase of reduction degree, shortening the time of complete conversion of oxygen carrier. Further analysis of chemical kinetics and reaction dynamics based on TGA curve showed that the Jander equation model was suitable for the reduction of Co-doped Fe2O3 at 344.7-391.0℃ and 414.7-472.5℃, and the Valensi equation model was suitable for the reduction at 607.6-681.5℃, according to which the kinetic parameters including activation energy and pre-exponential factor were also calculated. The research results could provide theoretical guidance for further application of CLC technology.
    Optimization and analyses of organic Rankine cycle combined system utilizing cold energy of LNG and industrial waste heat
    ZHANG Mogeng, ZHAO Liangju, LIU Chao, RAO Wenji, MO Yili, CAI Yilin
    2014, 65(8):  3144-3151.  doi:10.3969/j.issn.0438-1157.2014.08.040
    Abstract ( 429 )   PDF (697KB) ( 380 )  
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    For the use of low-temperature waste heat (about 150℃) and cold energy of liquefied natural gas (LNG, about -162℃), this paper presents a combined system. The thermodynamic and thermo-economy properties of the system are analyzed in detail, with comparative analysis on the proposed combined system and a separated system composed of a conventional organic Rankine cycle (ORC) and a low temperature ORC. Propane and R601a are adopted as work fluids in three cycles of the system, different temperature in internal heat exchanger and that in evaporator are selected to examine the system performance and obtain the best working condition. The results show that, for the combined system, the net work output increases 41.55%. The thermal efficiency and exergy efficiency are increased by 18.09% and 19%, while the area power ratio is only 61.03% of the separated system. The exergy lost among different components of the combined system is analyzed with the pressure exergy of LNG taken into account, and an appropriate system is proposed.
    Effects of temperature on pyrolysis products and characteristics of chrome shavings
    WANG Haining, ZHANG Shihong, LI Pan, YANG Haiping, WANG Xianhua, CHEN Hanping
    2014, 65(8):  3152-3158.  doi:10.3969/j.issn.0438-1157.2014.08.041
    Abstract ( 438 )   PDF (678KB) ( 271 )  
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    To provide experimental supports for resource utilization of chrome shavings, a small-scale external heated fixed bed pyrolyer was used to study the effects of temperature on its pyrolysis products and characteristics. The temperature range of experiment was 350℃ to 750℃. The results showed that the maximum liquid yield was 46.82% at 550℃. With rising temperature until to 750℃, gas yield increased significantly, and its calorific became also higher. The main ingredients in liquid product were N-and N/O-containing compounds. The oxygen content in liquid products decreased obviously with temperature increasing, and that of hexavalent chromium did rapidly and the most stayed in pyrolysis char. Organic functional groups in solid products decreased dramatically when the temperature getting higher, while carbon content increased.
    Catalytic effect of acidithiobacillus ferrooxidans and Fe3+ on microbial leaching process of MnO2
    ZHANG Xu, FENG Yali, LI Haoran, WANG Weida
    2014, 65(8):  3159-3163.  doi:10.3969/j.issn.0438-1157.2014.08.042
    Abstract ( 374 )   PDF (732KB) ( 315 )  
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    In the MnO2-FeS2-H2SO4 bacterial leaching system, the effects of acidithiobacillus ferrooxidans and Fe3+ alone or in combination on the leaching rate of Mn2+ from MnO2 were studied. The catalysis of acidithiobacillus ferrooxidans and Fe3+ in the system was analyzed by the cyclic voltammetric method. Acidithiobacillus ferrooxidans and Fe3+ alone or in combination could effectively increase leaching rate of Mn2+, and have some catalytic effect on the bacterial leaching process of MnO2. Electrochemical analysis showed that acidithiobacillus ferrooxidans and Fe3+ alone or in combination could cause obvious redox peaks of FeS2, and acidithiobacillus ferrooxidans could reduce the oxidation potential of FeS2 and decrease the difference in potential between FeS2 oxidation peak and reduction peak, thus catalyzing leaching of Mn2+ from MnO2.
    Biological treatment of high concentration NO2--N in passivation washing wastewater and process control strategy
    DONG Yijun, WANG Shuying, ZHANG Yukun, PENG Yongzhen
    2014, 65(8):  3164-3169.  doi:10.3969/j.issn.0438-1157.2014.08.043
    Abstract ( 339 )   PDF (1045KB) ( 318 )  
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    Biological treatment of high concentration NO2--N in passivation washing wastewater is difficult. In this paper nitrite oxidizing bacteria (NOB) was enriched by feeding NO2--N wastewater, NOB-rich activated sludge was used in an SBR system to treat simulated passivation washing wastewater, and a process control strategy was put forward. The results showed that using the process passivation washing wastewater with NO2--N concentration 2000 mg·L-1 could be totally oxidized within 300 min. The nitrite oxidation process was not inhibited by the high NO2--N concentration. Furthermore, this process had a correlation with the variation of DO concentration during reaction. DO-MSC, a parameter of the process control strategy, indicated the end of the reaction when it was more than 0.02. The results of batch tests showed that the DO-MSC could indicate the end of the nitrite oxidation process both in different aeration rates(0.02-0.125 m3·h-1) and different temperature(15-30℃).
    Electrochemical remediation of cadmium-contaminated soil enhanced by citric acid industrial wastewater
    GU Yingying, FU Rongbing, LI Hongjiang
    2014, 65(8):  3170-3177.  doi:10.3969/j.issn.0438-1157.2014.08.044
    Abstract ( 413 )   PDF (2980KB) ( 268 )  
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    Batch desorption and bench-scale electrochemical remediation experiments were conducted to investigate the feasibility of using citric acid industrial wastewater (CAIW) as the enhancement agent to extract cadmium from natural soil of high buffer capacity. The results of the desorption experiments indicated that it was very difficult to dissolve cadmium without any enhancement agent when the soil pH was above 7.0. The addition of CAIW, however, could make more than 85% of the sorbed cadmium dissolved into solution at pH≤5.0. The proportion of cadmium desorption was 20%-45% higher with the enhancement of CAIW compared with DI water at pH 5.0-8.0. The results of the electrochemical remediation experiments showed that CAIW as the electrolyte could cause significant migration of cadmium in soil compared with HNO3 solution of the same pH. Cadmium concentration in soil samples at 0-4 cm and 8-10 cm from the anode decreased to approximately 167-200 mg·kg-1 from the initial value of 282 mg·kg-1, while it increased to 400 mg·kg-1 at 4-8 cm from the anode. Approximately 84.7% of the spiked cadmium could be removed after 514 h of electrochemical treatment enhanced by CAIW. Approximately 94.6% of the removed cadmium was collected in the catholyte. It is concluded that CAIW can be a promising alternative for other expensive metal chelating agents for enhancing electrochemical remediation of heavy metal-contaminated soils of high buffer capacities.
    Experimental analysis on bio-fouling of iron bacteria on plate heat exchanger
    XU Zhiming, JIA Yuting, WANG Binglin, ZHANG Yilong, LIU Zuodong, WANG Jingtao
    2014, 65(8):  3178-3183.  doi:10.3969/j.issn.0438-1157.2014.08.045
    Abstract ( 685 )   PDF (1816KB) ( 347 )  
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    The bio-fouling characteristics of iron bacteria on plate heat exchanger was studied by several experiments to examine the impact of different flow velocity,temperature and concentration of iron bacteria. The results showed that the asymptotic value of heat transfer resistance of the plate heat exchanger, due to the bio-fouling, decreased gradually with increase of flow velocity. With increase of temperature,induction period of iron bacteria fouling cut down obviously,the rate of fouling accelerated,and the asymptotic value showed a reducing trend. With increasing concentration of iron bacteria, increase of the amplitude of heat transfer resistance of the plate heat exchanger was obvious because of the bio-fouling.
    Characteristic and mechanism of Cr3+ pollutant removal byKGM-base film
    CHEN Shuai, LIN Xiaoyan, LUO Xuegang
    2014, 65(8):  3184-3192.  doi:10.3969/j.issn.0438-1157.2014.08.046
    Abstract ( 343 )   PDF (8550KB) ( 279 )  
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    A new pollutant remover was prepared using Konjac glucomannan (KGM)-Acetate sol that was synthesized from KGM, acetic anhydride and auxiliary additives, and coated on the surface of lacquered metal polluted by Cr3+. The additives can make decontamination film fall automatically off after decontaminating. The influence of the synthesis conditions on rate of Cr3+ pollutant removal, that of KGM-Acetate sol concentration and film-forming temperature on film-forming time as well as that of various auxiliary additives on filmtearing strength were studied. FTIR, EDX and XPS were used to analyze the mechanism of Cr3+ pollutant removal. It is found that the time of film formation is the shortest 87 min at temperature 40℃ and pollutant removal concentration 4.7%. The experiment results show that at the condition of KGM 5 g, acetic anhydride 40 ml, reaction temperature 60℃and time 150 min, and volume of additive (sulfuric acid) 3 ml, the film-forming agent obtained KGM-Acetate sol has the maximum decontamination rate 99.2%. The removal of Cr3+ pollutant is likely to be attributed mainly by complexation interaction between Cr3+ and carbonyl oxygen in KGM-Acetate as well as physical adsorption. The tearing strength is the least for formulation of additive promoters citric acid 4 g:EDTA 6 g:sodium dodecylbenzenesulfonate 1 g:distilled water 89 g.
    Application of CO2 capture technology before burning in IGCC power generation system
    CHEN Xinming, SHI Shaoping, YAN Shu, FANG Fang, XU Shisen, DUAN Liqiang
    2014, 65(8):  3193-3201.  doi:10.3969/j.issn.0438-1157.2014.08.047
    Abstract ( 844 )   PDF (885KB) ( 468 )  
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    Integrated gasification combined cycle (IGCC) power generation is an advanced and next generation coal-fired power generation technology, can provide clean and low-cost electricity for the users, and will play an important role in the future development of high-efficiency and zero-emissions power plants. CO2 capture technology before burning should be very suitable for IGCC system. Based on IGCC technical features, a CO2 capture process before burning, consisting of MDEA acid gas removal and wet oxidation sulfur recovery steps, is proposed in this paper. The feasibility study of application in IGCC system is verified by process simulation calculation. The results show that this process works well for acid gas removal, and the efficiency for separating CO2 and H2S from syngas can reach 99% and 98.5% respectively. However, the overall efficiency of power supply by IGCC, obtained by calculation, declines about 10 percent from 45.35% to 35.16%, when the CO2 capture process before burning is introduced into IGCC system. The three main factors of decrease of total efficiency are steam consumption, fuel chemical energy loss and new auxiliary power increase, and they could be used for determining optimization direction.
    Photoelectric conversion performance of natural photosynthetic pigments from three typical members of purple bacteria for dye-sensitized solar cells
    FU Qiaoming, ZHAO Chungui, YANG Suping
    2014, 65(8):  3202-3211.  doi:10.3969/j.issn.0438-1157.2014.08.048
    Abstract ( 780 )   PDF (1092KB) ( 563 )  
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    The photovoltaic conversion systems based on photosynthesis have recently attracted much attention as alternative energy technology of the future. More interests are focused on the development of eco-friendly, cost-effective and safer dye-sensitized solar cells (DSSC)based on the principles and natural pigments of photosynthesis. Purple bacteria in anoxygenic phototrophic bacteria are good model systems for elucidating molecular mechanisms of photosynthesis. In this study, the photoelectrochemical properties of seven different natural photosynthetic pigments of bacteriochlorophyll a (BChl a) and carotenoids (Car) from Rhodopseudomonas palustris CQV97, Rhodobacter azotoformans R7 and Marichromatium sp. 283-1, and three modified BChl a derivatives were investigated in DSSC. The results showed that under the condition of simulated sunlight of 100 mW·cm-2 intensity and without addition of spacer, natural BChl a of 0.48 mg·ml-1 achieved better conversion efficiency of 1.26%. Purified rhodopin Car had higher conversion efficiency than that of mixture-Car and other purified Car. The absorption spectrum of TiO2 electrode sensitized by BChl a red-shifted, and the fluorescence at 800 nm could be quenched, indicating that the electron ejected by BChl a entered TiO2 conduction band. TiO2 electrode sensitized by co-sensitization of BChl a and rhodopin exhibited wide spectrum response in visible light and near-infrared region, the photocurrent and conversion efficiency of co-sensitized solar cells increased by 12% and 7.3% compared to BChl a. The photosynthetic pigments from purple bacteria are inexpensive and environment friendly, and are promising dye sensitizers due to higher light-harvesting capacity in near-infrared region. This study provides valuable information for fabricating visible light-infrared responsive solar cells.
    Influence of filter aid on MBR perfomance and fouling after high salt shock
    ZHANG Haifeng, YANG Liping, SONG L, ZHANG Lanhe
    2014, 65(8):  3212-3220.  doi:10.3969/j.issn.0438-1157.2014.08.049
    Abstract ( 389 )   PDF (1754KB) ( 253 )  
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    The main objective of this study was to investigate the effect of diatomite filter aid on fouling and performance of membrane bioreactor (MBR) after high salt shock. The results show that diatomite additive is an effective approach for the performance improvement of both membrane fouling and pollutants removal when MBR was suffering high salt shock. Compared with the control reactor, the performance of MBR is enhanced by addition of 60 mg·L-1 diatomite addition, the removal of COD, NH4+-N and TP increases by 4.9%, 3.2% and 74.5%, respectively. It was observed that after high salt shock the membrane fouling rate is significantly higher, about four-fold, for the contrast than for the MBR with diatomite addition. The flocculating and adsorption capacities of diatomite make soluble products of microbial metabolism (SMP) significant decrease. So, the rate of membrane fouling was significantly mitigated. Furthermore, the addition of diatomite makes mean flocs sizes (dp) and its related hydrophobic (RH) increase, which would be beneficial to the mitigation of membrane fouling.
    CCSEM investigation on slagging minerals in different density ingredients of bituminous coal samples
    WU Le, WU Jianqun, LUO Jia, CHEN Shihe, YU Dunxi, XIANG Chen, XU Minghou
    2014, 65(8):  3221-3227.  doi:10.3969/j.issn.0438-1157.2014.08.050
    Abstract ( 462 )   PDF (753KB) ( 315 )  
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    A typical bituminous coal that could easily lead to slagging was divided into three ingredients with different density, i.e. low-density (<1.3 g·cm-3), medium-density (1.3-1.6 g·cm-3) and high-density (>1.6 g·cm-3). Computer controlled scanning electron microscopy (CCSEM) was used to analyze and characterize the slagging minerals in the raw coal and three ingredients. The results showed that Na and K in inorganic minerals of the coal exist as aluminosilicate. Exterior (no bonding) pyrite and pyrrhotite with diameter larger than 22μm were mainly present in the high-density sample. The least proportion of unidentified materials in which there were the most particles containing 20%-90% of Fe component was involved in the high-density sample. The ratios of silicon to aluminum and basic to acidic oxides in bonding minerals were variation for different density samples. There was the highest basic to acidic oxides ratio in the low-density sample, suggesting highest slagging propensity. The ratios of silicon to aluminum and basic to acidic oxides were lower for the medium-density sample than for the raw coal.
    A new photovoltaic solar-assisted loop heat pipe/heat-pump system
    ZHANG Longcan, PEI Gang, ZHANG Tao, JI Jie
    2014, 65(8):  3228-3236.  doi:10.3969/j.issn.0438-1157.2014.08.051
    Abstract ( 580 )   PDF (2046KB) ( 345 )  
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    The photovoltaic solar assisted loop heat pipe system/heat-pump (PV-SALHP/HP) is the combination of solar assisted loop heat pipe system (SALHP) and solar assisted heat pipe (SAHP). A photovoltaic/thermal (PVT) evaporator and condenser could be shared by two circling modes, and so is the working medium. The loop heat pipe mode will be utilized when solar radiation is strong and the temperature of working medium in PVT evaporator is higher than that in condenser. Correspondingly, the heat pump mode will be started when solar radiation is weak or the temperature difference of working medium in PVT evaporator and condenser cannot satisfy the condition of loop heat pipe mode. The loop heat pipe mode is passive and the heat pump mode is active, which means that the loop heat pipe mode does not consume work and the heat pump mode does. Therefore, the transformable mode of system could heavily reduce power consumption, raise the utilization ratio of solar energy, and promote energy saving. A PV-SAHP/LHP test rig is built. The instantaneous and daily performance of the loop heat pipe mode and heat pump mode is studied.
    Pyrolysis of pubescens for high value-added chemicals
    MA Shanwei, LI Ming, CHEN Yixin, ZHU Xifeng
    2014, 65(8):  3237-3242.  doi:10.3969/j.issn.0438-1157.2014.08.052
    Abstract ( 490 )   PDF (523KB) ( 349 )  
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    In order to efficiently utilize bamboo resources and increase the yield of high value-added products, pyrolysis-gas chromatography-mass spectrometry(Py-GC/MS) was used to study the influence of temperature, time and pretreatment on pubescens pyrolysis. Temperature had an important effect on the pyrolysis process. With the increase of temperature in the range of 350-800℃, an increasing variety of products was obtained, and the total yield of products increased with the highest yield of target products at 600℃. The total yield of products increased with pyrolysis time until it reached a maximum. Alkali washing could improve the selectivity for phenols, but higher selectivity with stronger basic solution could decrease the yield of products after alkali washing.
    Agglomeration removal of fine particles at super-saturation steam by using acoustic wave
    YAN Jinpei, CHEN Liqi, YANG Linjun
    2014, 65(8):  3243-3249.  doi:10.3969/j.issn.0438-1157.2014.08.053
    Abstract ( 434 )   PDF (511KB) ( 276 )  
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    An experimental installation was set up for investigating experimentally agglomeration removal of dust particles under various steam super-saturation degrees by using acoustic wave. The results show that the acoustic wave entrainment coefficient for these fine particles goes up with increase of the super-saturation degree, leading to improvement of the removal efficiencies. When the super-saturation degree is below 1.0,the total removal efficiency of dust particles has almost no increase with it, and is quite low, about 10%. However, when the super-saturation degree is bigger than 1.0, the total efficiency can be promoted and goes up rapidly with the increase of super-saturation degree. For example, when the super-saturation degree increases from 1.0 to 1.5, the removal efficiency rises about 50%. The removal efficiency of dust particles increases also with rising sound pressure level. Even if at high sound pressure steam condensational growth can not occur yet at 0.3 of low steam super-saturation degree, hence, only low removal efficiency, less than 20%, is observed. But at 1.2 of high steam super-saturation degree, the removal efficiency can be significantly improved, for example at 130dB of lower sound pressure level, about 70% high efficiency can be obtained. These facts indicate that removal of dust particles can be effectively improved if acoustic wave is used, i.e. their agglomeration with steam can be enlarged.
    Effect of anode construction on performance of microbial fuel cells
    PAN Bin, SUN Dan, LIU Weifeng, YE Yaoli, GUO Jian, CHENG Shao'an
    2014, 65(8):  3250-3254.  doi:10.3969/j.issn.0438-1157.2014.08.054
    Abstract ( 446 )   PDF (1194KB) ( 283 )  
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    Biofilm on anode can influence anode's performance in microbial fuel cells(MFCs). Biofilm growth is influenced by anode surface area. The effect of anode structure on the maximum power output of MFC was investigated by changing lengths or numbers of carbon fibers as anode. For the length effect of carbon fiber anode, the highest maximum power density 10.50 W·m-2 is appeared at 1 cm-length. The maximum power density decreases sharply as the carbon fiber length further increase. When the anodes are constructed with different numbers of 2 cm-length of carbon fibers, the maximum power is proportional to amount of carbon fiber(s) (1-4 carbon fiber(s)). The maximum power for the anode with 4 pieces of 2 cm-length carbon fiber is 2.92 W·m-2, which is 2.78 times that generated with a single carbon fiber with the length of 8 cm. The biofilm on the carbon fibers surface could be observed by optical microscopy. The biofilm is much thicker at the place near current leading-out terminal than that at other parts of carbon fiber due to the resistance of the carbon fiber. These results indicate that increase of carbon fiber length can enlarge anode surface area, but can not significantly improve performance of anode.
    Kinetics analysis of ozone degradating 2,4-D pollutant in soil
    CHEN Lan, QUAN Yuheng, LI Zhiyong
    2014, 65(8):  3255-3260.  doi:10.3969/j.issn.0438-1157.2014.08.055
    Abstract ( 355 )   PDF (492KB) ( 300 )  
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    In order to control organic pollution in soil, ozone remediation of soil samples contaminated by 2,4-D(2,4-dichlorophenoxyl acid) was studied in a simulated soil columns. The effect of several factors such as addition of hydroxyl radical inhibitors, soil particle sizes, amount of O3 in O3-O2 mixed gas and moisture content in soil, on the kinetics of ozone remediation(2,4-D degradation) was investigated. To observe influence of water content on the kinetics, various volume of deionized water was added to the soil samles. The experimental results show that all ozone in gas-liquid phase, hydroxyl radicals in liquid-film and active sites on the surface of soil particles play roles in 2,4-D degradation in soil by ozone. For ozone remediation of moist soil there exist gas phase, liquid phase and solid phase, the contact between gas-liquid-solid phases is very important. The 2,4-D degradation by ozone follows the pseudo-first-order kinetics if reasonable simplification and hypothesis are added, and fitting correlation coefficients are higher than 0.9. A kinetic model of soil remediation proposed depends on soil water content. The experimental data reveal that the pseudo-first-order rate constants are fitted well with quadratic polynomial for the range of water content 0-9.38%(mass).
    Synthesis of poly(vinyl chloride)-butyl acrylate graft copolymer by ARGET ATRP method
    LIU Keyong, BAO Yongzhong
    2014, 65(8):  3261-3267.  doi:10.3969/j.issn.0438-1157.2014.08.056
    Abstract ( 573 )   PDF (613KB) ( 457 )  
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    The grafting copolymerization of butyl acrylate (BA) onto poly(vinyl chloride) (PVC) was conducted through the method of activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP), using PVC with higher labile chlorine content (U-PVC) and vinyl chloride/allyl 2-bromo-2-methylpropionate random copolymer (PVC-co-ABrMP) as an initiator. The polymerization conversion of BA was obviously increased as CuCl2 concentration (based on number of vinyl chloride unit) increased when CuCl2 concentration was lower than 0.1%. The increase of BA polymerization rate was not obvious when Sn(EH)2/CuCl2 molar ratio exceeded 50. The greater BA polymerization rate and PBA grafting degree were achieved when PVC-co-ABrMP was used as the initiator with the same catalyst. The side PBA chains were cleaved from the ester group of PVC-co-ABrMP and the molecular weight distribution index of PBA was 1.29, verifying the “living” nature of this graft copolymerization. The grafted PBA showed good internal plasticization effect on PVC, and the glass temperature of PVC-g-BA copolymer with 32.75%(mol) PBA was reduced to 8.34℃.
    Curing and pyrolysis behavior of PF/B4C/PBZ composite
    ZHANG Xiying, LIU Yuhong
    2014, 65(8):  3268-3276.  doi:10.3969/j.issn.0438-1157.2014.08.057
    Abstract ( 421 )   PDF (687KB) ( 751 )  
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    Phenol-formaldehyde resin (PF) has been widely used as an excellent thermosetting resin owing to its toughness, heat tolerance, chemical inertness and good electronic property. For high performance application, especially for expanding its usage in harsh environment demanding superior thermal and oxidation stability, further enhancement of the comprehensive properties is vital. Here, a thermally stable polyborazine (PBZ) and boron carbide ceramic microparticles (B4C) were incorporated simultaneously into the phenolic resin matrix. The curing kinetics and structure evolution of the PF/B4C/PBZ composite were investigated with differential scanning calorimetry (DSC), Fourier transform IR (FTIR) and thermal gravimetric analysis (TGA). Both the curing initiation and peak temperatures of the composite were lowered as a result of the presence of active hydrogen atom of PBZ and the hydrogen bonding among PBZ and PF. In addition, the thermal stability of PF was improved in the temperature range of 800-1000℃, with mass loss decreased from 18.2% to 5.6%, during pyrolysis with the synergistic modification of PBZ and B4C. Furthermore, after carbonization at 1550℃ for 2 h, graphitization of PF was enhanced and interlayer distance decreased from 0.3638 nm to 0.3494 nm due to the presence of PBZ and B4C. The strategy to high performance of PF via the combination of PBZ and B4C is feasible, and it allows a better way to modify the curing behavior without compromise to thermal stability.
    Extraction and characterization of SiO2 from rice-husk-char
    GU Jie, LIU Bin, FANG Fang, MA Zhongqing, ZHANG Qisheng, ZHOU Jianbin
    2014, 65(8):  3277-3282.  doi:10.3969/j.issn.0438-1157.2014.08.058
    Abstract ( 791 )   PDF (2943KB) ( 407 )  
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    The objective of this study is to develop a simple and green procedure for preparing SiO2 from rice husk char. The raw material, rice husk char from downdraft fixed bed gasification was used to extract SiO2 by adding K2CO3. To find the influence of extraction and aging conditions on SiO2 yield, the experiments were conducted. The results showed that the optimum conditions were as follows: the impregnation ratio of K2CO3 solution (mass fraction of 20%) to rice husk char was 3.0, the extraction time 3.5 h. The temperature and time of aging was 3℃ and 3 h, respectively. At these conditions, SiO2 yield was 25.89% and purity 97.02% after acid treatment. The structure and property of SiO2 were analyzed using SEM, EDX, and XRD. The results indicated that it could be a practical way for the high efficiency, environmental-friendly and resource utilization of rice husk char.
    Alicyclic epoxy resin cured by thermal frontal polymerization
    ZHOU Jianping, ZHAO Haifang, WU Huiru, LIU Zhilei, JIA Shijun
    2014, 65(8):  3283-3289.  doi:10.3969/j.issn.0438-1157.2014.08.059
    Abstract ( 485 )   PDF (954KB) ( 406 )  
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    The method of thermal frontal polymerization (TFP) was used to cure the selected alicyclic epoxy resin. The effect of the factors, including amount of curing agent, preheating temperature and tilt angle of reactor, on frontal velocity and frontal temperature was investigated. The structure and thermal properties of the cured products were characterized with FTIR, DSC and TG analysis. The results showed that both frontal velocity Vf and maximum frontal temperature Tmax increased with increasing amount of curing agent or preheating temperature, while initiation time and the time needed to reach the highest frontal temperature decreased. When the reactor tilted, the heading direction of the descending front would drift, and frontal velocity would tend to slow down. The analysis of FTIR spectrum indicated that the products obtained by the TFP method exhibited similar infrared absorption as compared to that of the products prepared by the traditional thermal curing method. DSC and TG results revealed that the products obtained by the TFP method had higher glass transition temperature and better thermal stability.
    Synthesis and performance of SAS/MAA/MPEGMAA polycarboxylate dispersants
    ZHANG Guanghua, QU Qianqian, ZHU Junfeng, WANG Peng, FU Xiaolong, WEI Yingfei
    2014, 65(8):  3290-3297.  doi:10.3969/j.issn.0438-1157.2014.08.060
    Abstract ( 737 )   PDF (739KB) ( 402 )  
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    The esterified macromonmer (MPEGMAA) was obtained by esterification ofmethoxy polyethylene glycol (MPEG)withfour kinds of different side chain lengthsand methacrylic acid (MAA).Four kinds of different side chain lengths of polycarboxylate dispersants were prepared from esterified macromonmer (MPEGMAA), methacrylic acid (MAA), allyl sulfonate (SAS) as monomers, potassium persulfate (K2S2O8) as initiator and hydroquinone as inhibitor. Their structures, molecular weights and distributions were characterized and analyzed by FT-IR, 1H NMR and gel permeation chromatography (GPC). The dispersants were used for Binchang coal, and apparent viscosity, rheology, zeta potential, adsorption, maximum slurry concentration and stability of the slurry were investigated. The contact angles between coal surface and dispersant were measured, and the surface of coal particles after adsorbing the dispersant with was analyzed with X-ray photoelectron spectroscopy (XPS), with the thickness of adsorption layer of 6.12 nm. The polycarboxylate dispersant with the length of side chain SAS/MAA/MPEGMAA750 showed good wetting and adsorption, as well as better function of viscosity reduction, dispersion and stabilization on Binchang coal.
    Preparation and electrochemical performances of in-situ Ni/Al-LDH/MCNTs composites
    LI Yanwei, LIANG Xiaoli, YAO Jinhuan, JIANG Jiqiong
    2014, 65(8):  3298-3305.  doi:10.3969/j.issn.0438-1157.2014.08.061
    Abstract ( 626 )   PDF (1561KB) ( 434 )  
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    Ni/Al-LDH/MCNTs composites with MCNTs contents of 1%, 3%, and 5% were prepared by the in-situ homogeneous precipitation method with Ni(NO3)3·6H2O, Al(NO3)3·9H2O, urea, and MCNTs as raw materials. The microstructure and morphology of the Ni/Al-LDH/MCNTs composites were analyzed with X-ray diffraction (XRD), Fourier transform infrared (FTIR) and field emission scanning electron microscopy (FESEM). The electrochemical performance of the Ni/Al-LDH/MCNTs composites used as cathode materials for nickel-hydrogen battery were characterized with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge tests. The results demonstrated that the introduction of MCNTs could enhance electrochemical activity, decrease electrochemical reaction resistance, and significantly improve high rate performance of Ni/Al-LDH. In particular, the Ni/Al-LDH/MCNTs composite with MCNTs content of 3% had the best electrochemical performance. For example, the specific discharge capacities of the Ni/Al-LDH/MCNTs composite with MCNTs content of 3% under current densities of 200, 500, 1000, and 2000 mA·g-1 were 330, 321, 307, and 288 mA·h·g-1, respectively. While for the Ni/Al-LDH without MCNTs, the specific discharge capacity was only 205 mA·h·g-1 under the current density of 2000 mA·g-1.