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Table of Content
05 May 2016, Volume 67 Issue 5
    CIESC Journal(HUAGONG XUEBAO)Vol.67 No.5 May 2016
    2016, 67(5):  0-0. 
    Abstract ( 51 )   PDF (1248KB) ( 465 )  
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    Research progress on photocatalytic degradation of organic pollutants by graphene/TiO2 composite materials
    LIU Fang, FAN Fengtao, LÜ Yucui, ZHANG Shuang, ZHAO Chaocheng
    2016, 67(5):  1635-1643.  doi:10.11949/j.issn.0438-1157.20151581
    Abstract ( 491 )   PDF (1553KB) ( 1713 )  
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    Graphene is a new kind of carbon nano-materials with a large specific surface area and excellent electrical conductivity. When it is incorporated into TiO2 semiconductor to form a composite materials, TiO2 photocatalytic performance could be greatly enhanced and the composite has extensive application prospect in the field of photocatalysis. Graphene in titanium dioxide/graphene nanocomposites can promote effectively separation of electron and hole, and enhance the absorption efficiency of TiO2 surface for organic pollutions in certain extent. In this review, the preparation methods of graphene /TiO2 composite nanomaterials and their application in photocatalytic degradation of organic pollutants are reviewed. And the mechanism of photocatalytic enhancement by graphene/TiO2 composites is also analyzed. Finally, the future prospect on the trends of graphene/TiO2 composite photocatalyst is also given.

    Chemical properties and characterization methods for hydrothermal liquefaction bio-crude from microalgae: a review
    ZHANG Jixiang, JIANG Baohui, WANG Dong, WEI Yaodong
    2016, 67(5):  1644-1653.  doi:10.11949/j.issn.0438-1157.20151582
    Abstract ( 181 )   PDF (2158KB) ( 447 )  
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    Hydrothermal liquefaction (HTL) bio-crude from microalgae cannot be directly used as transportation fuels due to poor quality. A new approach for its application is integration of it and modern petroleum processing industry. The chemical properties of HTL bio-crude, including chemical composition, functional groups and heteroatom compounds constitution are summarized in this paper. The characterization methods including GC-MS, FTIR, NMR, FT-ICR MS were compared and analyzed. Formation mechanism and upgrading of HTL bio-crude were also briefly reviewed. The focus is on higher oxygenated and nitrogenous compounds content in HTL bio-crude, higher aromaticity and unsaturation degree comparing with heavy crude oil or residue oil. Catalytic hydrotreating could effectively remove heteroatom and increase hydrocarbon content. The development of microalgae-based bio-fuels depends on not only the progress in upgrading technique but also the improvement of characterization methods.

    Advances in sexual hormone trisporic acid biosynthesis in carotenoids producing Blakeslea trispora
    ZHANG Xiaohui, SU Sisi, WANG Wenya, YUAN Qipeng, LI Qiang
    2016, 67(5):  1654-1664.  doi:10.11949/j.issn.0438-1157.20151591
    Abstract ( 74 )   PDF (723KB) ( 217 )  
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    Given that carotenoids are important fine chemicals, the Blakeslea trispora is receiving increasing attention since its higher industrial production of carotenoids. Numerous factors could affect the carotenoids production in Blakeslea trispora, among which the trisporic acid is one of the uttermost importance. In the present paper, the advances of biosynthesis of trisporic acid were reviewed, including summary of carotenoids production by fermentation, structure and biological function of trisporoids, biosynthetic pathway of trisporic acid and molecular biology of trisporic acid biosynthesis.

    Characterizing of thermal conductivity and thermal diffusivity of methane hydrate by free-standing sensor 3ω method
    YAO Guice, YUAN Kunpeng, WU Shuo, WANG Zhaoliang
    2016, 67(5):  1665-1672.  doi:10.11949/j.issn.0438-1157.20150930
    Abstract ( 143 )   PDF (635KB) ( 224 )  
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    Most experiments about gas hydrates were based on time domain. With the development of the free-standing sensors based on 3ω method, the thermal conductivity and thermal diffusivity of methane hydrate could be easily measured in frequency domain. Experimental devices for synthesis of methane hydrate under low temperature and high pressure was established and the thermal contact resistance (TCR)was measured. Besides that, the temperature dependence of thermal conductivity and thermal diffusivity for methane hydrate was analyzed and the measurement value was compared with the data printed by others. It was found that the TCR had a great effect on measurement data. The values omitting TCR tended to be closer to the true value when the TCR became lower.

    Measurement of vapor-liquid equilibrium data and azeotropic analysis for 2,4-toluene diisocyanate +entrainer
    XU Mian, WU Liangheng, ZHANG Jie
    2016, 67(5):  1673-1679.  doi:10.11949/j.issn.0438-1157.20150433
    Abstract ( 109 )   PDF (509KB) ( 493 )  
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    When conducting the removal process of free toluene diisocyanate(F-TDI)from polyurethane prepolymer by azeotropic distillation, the isobaric vapor-liquid equilibrium (VLE) data and basic thermodynamic parameters for 2,4-TDI + entrainer are missing. Isobaric VLE data for 2,4-TDI/ethyl benzoate(EBZ), 2,4-TDI/diethyl succinate (DES) and 2,4-TDI /dimethyl adipate (DMA) were measured at 0.55 kPa by using a self-made recirculation still. The binary VLE data have passed the thermodynamic consist test proposed by the area method. The parameters and regression deviations for the UNIQUAC equation were obtained by data regression with simulation system of Aspen Plus. The average deviations of vapor mole fraction were 0.0067, 0.0083 and 0.0179, and the average absolute deviations of the predicted temperature were 0.7 K, 1.2 K and 0.5 K for the three groups, respectively. Furthermore, azeotropic systems were analyzed, and the azeotropic compositions and azeotropic conditions were provided for the azeotropic distillation of F-TDI separation.

    Thermophysical properties of HFE7100 and HFE7500
    BI Shengshan, CUI Junwei, MA Lunjian, ZHAO Guanjia, WU Jiangtao
    2016, 67(5):  1680-1686.  doi:10.11949/j.issn.0438-1157.20151505
    Abstract ( 206 )   PDF (466KB) ( 283 )  
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    Due to their favorable thermophysical and environmental properties HFE7100 and HFE7500 are extensively applied as heat transfer fluids in semiconductor industry and cleaning solvents in electronic components. Thermal conductivity of HFE7100 and HFE7500 under atmospheric pressure was measured by a transient hot-wire technique, as well as their liquid viscosity and surface tension by the surface light scattering (SLS) method. Thermal conductivity and liquid viscosity were correlated with temperature as polynomial functions. The average absolute deviations between correlations and experimental data of thermal conductivity and liquid viscosity are 0.37% and 1.19% for HFE7100, and 0.08% and 1.10% for HFE7500, respectively. A modified correlation based on van der Waals was used for that of surface tension as a function of temperature, by which the average absolute deviations of surface tension are 0.03 and 0.02 mN·m-1 for HFE7100 and HFE7500, respectively. In this study, the experimental and correlation data of conductivity, viscosity and surface tension can be supportive for engineering application.

    Determination and graphics expression of ice-salt eutectic points of multicomponent salt-water systems
    WANG Xueying, HUANG Wenting, HUANG Xueli
    2016, 67(5):  1687-1693.  doi:10.11949/j.issn.0438-1157.20151485
    Abstract ( 162 )   PDF (561KB) ( 386 )  
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    For the quaternary salt-water systems, such as the homo-ion system K+//Cl-, SO42-, NO3--H2O and interaction system Na+, K+//SO42-, NO3--H2O, as well as their six ternary subsystems, the freezing points, eutectic points and the crystallization regularities of salts were studied by cooling method. According to experimental data, the eutectic point temperature-liquid composition diagrams for these systems were plotted. The results were as follows: (1) The crystallization regularity of salts and the eutectic point temperatures can be obtained by measuring the time-temperature curves for multicomponent salt-water systems during cooling process; (2) In these systems above, 3K2SO4·Na2SO4 existing under normal temperature did not appear at the eutectic point temperature. As a result, the phase relationships in these systems were simplified; (3) The prism can be used to describe the relationships among the phases, freezing points or eutectic points and the compositions of liquids for the ternary systems, the quaternary homo-ion systems and interaction systems concisely and visually; (4) In the eutectic point temperature-liquid composition diagrams, for ternary systems without double-salts, there were two eutectic curves with single salt and ice, one eutectic point with two salts and ice, and one ice crystallizing region. For the quaternary homo-ion systems and interaction systems, there were three and four eutectic regions with single salt and ice, three and five eutectic curves with two salts and ice, and one and two eutectic points with three salts and ice, respectively.

    Efficient estimation of axial mixing distribution for extraction in rotating disc contactor based on simulation using mean age theory
    CHEN Hang, SUN Ze, SONG Xingfu, YU Jianguo
    2016, 67(5):  1694-1700.  doi:10.11949/j.issn.0438-1157.20151476
    Abstract ( 116 )   PDF (8451KB) ( 157 )  
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    In this study, on basis of verification of single-phase flow field simulation by computational fluid dynamics (CFD), the mean age theory was employed to estimate axial mixing distribution in a pilot-scale rotating disc contactor (RDC). In order to validate the mean age theory, two results of theoretical mean residence time and the simulated values by species transport model were compared. It showed that the mean age theory is capable to relatively accurately predict the axial mixing distribution in RDC within ten seconds of computional time, far shorter than two weeks by traditional species transport model, hence possesses the advantage of low computational cost. Moreover, the mean age theory is also capable to provide the spatial distribution information of axial mixing distribution, while the traditional species transport model does not. Hence, the mean age theory can provide more information for structural optimization, and is an efficient method to calculate the axial mixing distribution for extraction. Subsequent analysis on hydrodynamics in RDC showed that it is appropriately mixed flow in compartments and plug flow between compartments, which is favorable for extraction operation. Compared with the well mixing between rotors, the flow field between stators has apparent dead flow zones, which are mainly attributed to two factors of low flow velocity and cyclic vortex structure. The dead zones cause a certain flow non-idealities and are disadvantage for extraction efficiency. Hence, the structure of the stators in RDC needs to be further improved.

    CFD simulation and backflow analysis of combined directed valve tray
    LIU Jianglin, ZHANG Jiexu, JI Lijun, CHEN Kui, WU Bin, WU Yanyang, ZHU Jiawen
    2016, 67(5):  1701-1709.  doi:10.11949/j.issn.0438-1157.20151376
    Abstract ( 481 )   PDF (7605KB) ( 239 )  
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    The flow patterns and hydraulics of gas-liquid flow on a commercial scale distillation tray is of great importance in determining the tray efficiency. Based on experimental data, a new correlation of average gas hold-up was fitted and built in the inter-phase momentum transfer source for CFD simulations. The simulations of combined directed valve trays of 1.2 m air-water system were carried out by Fluent, a commercial CFD software, and the flow pattern characteristics was investigated. The clear liquid height determined from CFD simulations was in good agreement with the predicted results calculated from the correlation in this work, which proved the validity of simulations. Non-ideal flow of liquid phase on the trays was quantified by the backflow volume ratio T, the ratio of backflow volume to total grid volume. The time-averaged values of the backflow volume ratio (Tav) of 3 tray patterns with different arrangements of trapezoidal and rectangular directed valves were calculated respectively. The results showed that the different arrangements of two kinds of valves had remarkable influence on volume fraction of backflow. By reasonable arrangement, Tav could reduce from 22.0% to 19.4% with the decreased backflow volume by 11.8% compared to the industrial tray. This study was expected to provide a guidance for the tray design and optimization.

    Discrete modeling of discharge dynamics of granular material in moving bed: effect of outlet setting
    XIAO Xiao, SU Jinglin, XU Guangwen, CUI Lijie, LIU Xiaoxing
    2016, 67(5):  1710-1718.  doi:10.11949/j.issn.0438-1157.20151714
    Abstract ( 159 )   PDF (1637KB) ( 295 )  
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    The influence of outlet setting on the discharge dynamics of granular material in 2D moving beds was investigated by conducting discrete element simulations. To validate the simulation, a moving bed with single outlet was first modeled. The simulation results showed that the variation of discharge rate was tally with the modified Beverloo, and the variation tendency of the width of funnel zone was in agreement with the experimental data. Based on such validation, the discharge characteristics of granular material in the moving bed with two outlets were then systematically investigated. The simulation results indicated that as to the bed with two same size outlets, the width of funnel zone was simply equal to the sum of the width of funnel zone of the moving bed with one same size outlet, the distance between outlets and the width of outlet, and the granular mass discharge rate was roughly equivalent to that of the moving bed with one same size outlet. For the bed with two different size outlets, increasing the width of large outlet or decreasing the outlet distance was conducive to increasing the discharge rate at small outlet. Nevertheless, the discharge rate at large outlet was not influenced by the small outlet and nearly kept constant.

    Effect of mixing chamber diameter on performance of transcritical CO2 heat pump system with ejector
    WEI Jin, TANG Liming, QI Haiming, CHEN Qi, CHEN Guangming
    2016, 67(5):  1719-1724.  doi:10.11949/j.issn.0438-1157.20151268
    Abstract ( 122 )   PDF (517KB) ( 264 )  
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    The use of ejectors is one of the most promising methods to recover the throttling loss of transcritical CO2 heat pump systems. Experimental investigation on the effect of mixing chamber diameter on the performance of transcritical CO2 heat pump system with ejector was carried out. The mixing chamber diameter was 1.2, 1.4 and 1.6 mm, respectively. The hot water inlet temperature, as well as the evaporating temperature was kept constant in all experiments. Hot water outlet temperature as a variable was chosen to be the comparison reference of the experiments. The results showed that the effect of the mixing chamber diameter on the compressor exhaust temperature was relatively small. However, the diameter has a significant effect on the compressor exhaust pressure. The system with 1.6 mm mixing chamber diameter had the lowest compressor exhaust pressure and the highest heating coefficient of performance (COP). Moreover, for the performance of the ejector, the mixing chamber diameter had a greater effect on the entrainment ratio than the pressure lift ratio.

    Simulation of flow-reaction process in fluidized bed gasifier considering particle rotational motion
    WANG Zhiyu, HAO Zhenhua, DONG Libo, LI Junguo, LU Huilin
    2016, 67(5):  1725-1731.  doi:10.11949/j.issn.0438-1157.20151663
    Abstract ( 128 )   PDF (693KB) ( 733 )  
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    Abandoning the pure smooth assumption of particles in classical kinetic theory of granular flow, this work established a kinetic theory model for rough granular and provided relevant constitutive correlations with approximate solutions by considering both opposite and tangential components force of the rough granular. Combined with the gasification model of coal powders, the flow-reaction process of coal powders was simulated in a bubbling fluidized bed and the time-average velocity and particle concentration distributions with rough granular were obtained in the bed. The simulated fluctuating energy and heterogeneity of rough granular in the fluidized bed increased compared with the simulated results of the smooth particles. The concentration of gas components obtained in the simulation agreed well with the experimental data in the literature.

    CPFD simulation on heat transfer mechanism of vertical tube in bubbling fluidized bed
    WEI Qing, YAO Xiuying, ZHANG Yongmin
    2016, 67(5):  1732-1740.  doi:10.11949/j.issn.0438-1157.20151335
    Abstract ( 98 )   PDF (657KB) ( 223 )  
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    Based on the previous experimental study, a computational particle fluid dynamics (CPFD) model was used to reveal the heat transfer mechanism between a vertical heat tube and a fluidized bed of fine FCC particles. Emphasis was put on the hydrodynamics related to the particle renewal on the heat tube surface. The relationships between the gas-solids hydrodynamics on the heat tube surface and the local heat transfer properties were discussed. The predicted total particle renewal fluxes and packet mean residence time according to the packet renewal model at different superficial gas velocities and radial positions can both explain the change of the measured heat transfer coefficients, which indicates the dominant role of the particle renewal on the bed-to-wall heat transfer in a bubbling fluidized bed. As the heat tube moves from the bed center to the column wall, there is an increasing tendency for the circumferential non-uniformities of both solids renewal flux and heat transfer coefficient. As the superficial gas velocity increases, the internal solids circulation flux in the bed increases as a result of stronger bubble movement, which is the root cause of the strengthened solids renewal on the heat tube surface and the increased heat transfer coefficient.

    Diffusion coefficient of solid particles in turbulent fluidized bed
    ZHOU Bihui, ZHAO Ming, LIANG Junyu, LU Yong, XIAO Rui
    2016, 67(5):  1741-1747.  doi:10.11949/j.issn.0438-1157.20151492
    Abstract ( 121 )   PDF (4414KB) ( 240 )  
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    Based on particle image velocity (PIV) technology and particle diffusion law, the diffusion coefficient of SAPO-34 catalyst particles in turbulent fluidized bed for methanol to olefins (MTO) was studied. A two dimensional transparent glass fluidized bed reactor was used to study the particle diffusion coefficient as functions of operating gas velocity and particle size. The motion of SAPO-34 particles was recorded by high speed camera, based on which both longitudinal and lateral velocities were calculated via image processing technology, hence the diffusion coefficient was obtained according to particle diffusion law. It showed that both longitudinal and lateral diffusion coefficient of SAPO-34 particles (Geldart A) increased with operating gas velocity. The longitudinal diffusion coefficient ranged from 10-3 m2·s-1 to 10-2 m2·s-1, and the lateral diffusion coefficient from 10-1 m2·s-1 to 10-2 m2·s-1. In addition, under the same fluidization operating gas velocity, the particles with smaller particle size possessed larger diffusion coefficient than those with larger one. It is of significance for the research related to the motion law of particles in turbulent fluidized bed.

    Numerical simulation of condensation in horizontal circular and square minichannels using R134a
    ZHANG Jingzhi, LI Wei
    2016, 67(5):  1748-1754.  doi:10.11949/j.issn.0438-1157.20151306
    Abstract ( 115 )   PDF (618KB) ( 182 )  
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    Heat transfer and pressure drop characteristics of condensation for R134a at saturation temperature of 320 K inside horizontal circular and square minichannels were investigated numerically. The results indicated that the heat transfer coefficients and frictional pressure drop gradients increased with mass flux and vapor quality, while the pressure drops decreased with increasing vapor quality at x>0.85. Compared with the circular tube, the square channel with the same perimeter as the corresponding circular tubes can enhance heat transfer coefficients and increase the pressure losses. The numerical results agreed well with the well-known empirical correlations for condensation. A thicker liquid film was obtained at the bottom of the round tube, while the liquid film for the square channel accumulated at the bottom and the middle top of the channels at lower vapor quality. The proportion of the thinner liquid film region, which corresponded to a higher heat transfer coefficient, increased with increasing vapor quality, leading to a higher heat transfer coefficient at higher vapor quality. The liquid film thicknesses in square channels were lower than that in circular channels, thus enhancing the heat transfer.

    Start-up performance of novel horizontal loop thermosyphon
    ZHU Zhen, WANG Yinfeng, XIONG Guohui, FAN Hongtu, ZHU Yuezhao
    2016, 67(5):  1755-1761.  doi:10.11949/j.issn.0438-1157.20151316
    Abstract ( 69 )   PDF (1168KB) ( 211 )  
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    Thermosyphon has begun to be used in the midium-high temperature trough type solar energy heat utilization system. The characteristics of the solar radiation makes a great influence on the solar collection efficiency in the start-up performance of thermosyphon, and thus solar collecting performance changes. The novel horizontal loop thermosyphon (HLTS) with the dowtherm has been developed. The platform has been set up to test the influence of filling content, heat flux and ambient temperature to the start-up performance of the HLTS. As the result, the direction flow of steam in the evaporator of HLTS is single and the filling content has influenced the operation of heat pipe. The best filling content of injection is 3.325 kg, and the pulsating flow forms in the evaporator when the ratio is 100%. The start-up time changes short when the heat flux increases in the same filling, while the start-up temperature of HLTS does not change and keeps in the temperature of 150℃ when the filling content is 3.325 kg. The best heat flux is 7.619 kW·m-2 as the NHLT used in the solar collector. Moreover, the low temperature makes the oil frozen in the evaporator at below 9℃ with extending time of the start-up of thermosyphon.

    Friction characteristics for water-ethylene glycol mixture flow in horizontal tubes with new type of helically fins
    ZHANG Jili, WANG Yonghui, MA Zhixian, CHEN Jingdong
    2016, 67(5):  1762-1770.  doi:10.11949/j.issn.0438-1157.20151514
    Abstract ( 84 )   PDF (1081KB) ( 125 )  
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    An experiment setup was built for investigating single-phase adiabatic flow characteristics of internal helical-rib roughness. The friction characteristics for 15% (by volume) water-ethylene glycol mixture flow in three internal finned tubes (two types of new developed internal helical-fins) and a smooth tube were obtained. The parameters of test tubes are nominal inside diameters (22 mm and 16 mm), numbers of fins (60 and 38), helix angles (45° and 60°) and fin height to inside diameter ratios (0.022 and 0.053). The lengths of the internal helical-rib tubes in test section were 2643 mm and 2945 mm, respectively. The Prandtl number varied from 13.9 to 23.2 and the Reynolds number ranged from 4000 to 33000. The smooth-tube results were compared to the Filonenko equation with satisfactory agreement. The experimental results of different length and same type multi-start internal helically-finned tubes also showed that the entrance effect on the friction factor in the multi-start internal helically-finned tube increased with the increase of Re. Especially for Re>20000, the criterion that entrance effect can be ignored when lo/di>60 (lo—length in test section, di—inside diameter) was not suitable for the multi-start internal helically-finned tube. All the three helically-finned tubes results indicated that there was a critical Re, Recr, a function of geometric variables of internal helically fins. The friction factor achieved the maximum when Re=Recr and for 4000<Re<Recr. The earlier friction factor correlations could not be in good agreement with experimental data. Much efforts should be done to enlarge the application range of the earlier empirical formula. Also, for 4000<Re<Recr, the variation tendency of friction factors in multi-start internal helically-finned tubes were greatly different from those in equivalent roughness tubes used in the Nikuradse experiment. The difference between resistance mechanisms of internal helically-finned tube and artificial equivalent roughness tube was analyzed and deserved more attention.

    Evaporation characteristics of spray flash evaporation at high temperature and high pressure
    JI Can, WANG Naihua, CUI Zheng, CHENG Lin
    2016, 67(5):  1771-1777.  doi:10.11949/j.issn.0438-1157.20151702
    Abstract ( 97 )   PDF (1027KB) ( 237 )  
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    The influence of initial and operating conditions on spray flash evaporation characteristics was investigated based on a new high-temperature and high-pressure spray flash evaporation system. Water was used as the working fluid. The initial liquid temperature was raised to above 100℃ and the pressure inside the flash chamber was maintained positive for the first time. A specially-designed swirl nozzle with two S-shaped internal vanes was used to inject liquid upward or downward into the flash chamber. The experiments were conducted at initial temperatures ranging from 135 to 150℃, pressures of 121, 126, 131, 136, 141 and 146 kPa and superheats from 30 to 46℃. The results indicated that the mass flow rate of vapor generated by flashing increased with the increase of initial temperature and decreased with the increase of pressure. Downward injection outperformed upward injection for higher vapor generation rate and less water carried out by vapor. The flash efficiency was found to increase linearly with the degree of superheat. An empirical equation between flash efficiency and the degree of superheat was proposed based on a large amount of experimental data. The results provided reference for the application of spray flash evaporation at high temperature and high pressure in industrial fields.

    Transient properties of bifacial evaporator loop heat pipe
    HE Song, LIU Zhichun, WANG Dongdong, LIU Wei, YANG Jinguo, ZHANG Xiaoyu
    2016, 67(5):  1778-1783.  doi:10.11949/j.issn.0438-1157.20151669
    Abstract ( 101 )   PDF (895KB) ( 249 )  
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    Loop heat pipe (LHP) is an efficient two-phase heat transfer device, mainly applied to spacecrafts and terrestrial electronics with high heat density. The existing flat loop heat pipes (FLHPs) are only used a surface to dissipate heat. Thus, the adverse back-conduction makes it difficult for FLHPs to startup at low heat loads, and also, the another surface of the flat evaporator possesses the potential for heat rejection. Aiming at the disadvantages above, a methanol-copper loop heat pipe with a bifacial evaporator was developed in this paper. Under the conditions of assisted-gravity angle at 10° and heat sink temperature at 0℃, startup performance and variable heat load operation were investigated with one surface heated and two surfaces heated simultaneously. The experimental results indicated that this loop could start up successfully and operate normally when one surface or two surfaces worked, but startup process with two surfaces heated showed faster and more stable. With heat source simulator wall temperature below (90±2)℃, the evaporator with one surface heated could transfer the maximum heat load of 210 W, corresponding to a heat flux of 21.8 W·cm-2, while 240 W at the evaporator with two surfaces heated. For operation with alternative heat load, the LHP could quickly shift from one surface to another surface, and operation failure was not observed.

    Analytical and numerical studies on apparent viscosity in coaxial cylinder rotational rheometer during initial unsteady stage
    XU Ruiyu, LIU Gang, CHEN Lei, TENG Houxing, LU Xingguo, XU Jikai
    2016, 67(5):  1784-1790.  doi:10.11949/j.issn.0438-1157.20150865
    Abstract ( 89 )   PDF (545KB) ( 166 )  
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    During the initial testing stage with controlled stress or controlled shear rate, apparent viscosity is much higher than its true value because of factors such as transient flow process. Most existing researches about Couette flow in the measuring gap of coaxial cylinder rotational rheometer focus on constant boundary or time-dependent boundary in special form, which may has a gap with the actual changing boundary condition within rheometer. Thus, the arbitrary moving boundary condition was taken as f(t), and the transient flow was simplified in coaxial cylinder for Couette flow into two infinite parallel plates. The exact solutions of apparent viscosity and velocity under controlled stress boundary and controlled shear rate boundary were derived through eigenfunction method and Laplace transform. Meanwhile, the numerical calculations of apparent viscosity under six boundary conditions were made according to two kinds of gap size and different viscosity (2—200000 mm2·s-1). It showed that when the viscosity of newton fluid was below 20 mm2·s-1, the equilibrium of flow and apparent viscosity under controlled shear rate boundary cost less time. When the viscosity was among 20—20000 mm2·s-1, the equilibrium under controlled stress boundary cost less time. However, the equilibrium time under two kinds of boundary was nearly the same when the viscosity was over 20000 mm2·s-1.

    Effect of coiling ways of inertance tube on performance of pulse tube cryocooler
    LIU Shaoshuai, ZHANG Ankuo, CHEN Xi, KAN Ankang, JIANG Yanyang, ZHANG Hua, WU Yinong
    2016, 67(5):  1791-1797.  doi:10.11949/j.issn.0438-1157.20151124
    Abstract ( 112 )   PDF (2819KB) ( 244 )  
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    To study the influence of inertance tube coiled in the performance of pulse tube refrigerator and reveal the variation of phase shifting of inertance tube and cooling performance of different coiled structure, the pressure drop in the inertance tube coiled was calculated and the turbulence was considered. The pressure drop rose up and the phase angle decreased with increasing coiled numbers. Then, a pulse tube cryocooler with different coiled inertance tubes was tested. With the same cooling power, the compressor efficiency decreased while increasing coiled numbers. The research will be an excellent reference for engineering application of the inertance pulse tube cryocooler.

    Influence of non-uniform heat flux on performance of thermoelectric device
    MING Tingzhen, PAN Tao, WANG Qiankun, ZHOU Junli, YANG Wei, GONG Tingrui
    2016, 67(5):  1798-1805.  doi:10.11949/j.issn.0438-1157.20151409
    Abstract ( 112 )   PDF (2907KB) ( 273 )  
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    An effective approach to increase the output power efficiency of thermoelectric devices is to increase the temperature difference between the hot and cold ends of thermoelectric devices. However, when the heat flux being imposed upon the hot end is non-uniform, the temperature distribution on the hot surface is uneven, which will influence the overall performance of the device. Based on this, a conjugate thermal to electric energy conversion mathematical model of thermoelectric devices was established to analyze the influences of thermoelectric material properties, non-uniform heat flux on the output power performance of thermoelectric device. Numerical simulation results indicated that the influence of temperature dependent material properties on the system output power cannot be neglected and the influence on the system maximum temperature difference will approach 4% when heat flux is about 4 W·cm-2. The non-uniform heat flux has significant influence on the output power of thermoelectric device. The less the uniformity of heat flux upon the hot end of thermoelectric device, the more uneven of temperature distribution on the hot end, the maximum temperature, the high temperature region and the open-circuit voltage will be.

    Numerical simulation of wet steam non-equilibrium condensing flow in cascade passage
    HAN Zhonghe, HAN Xu, LI Hengfan
    2016, 67(5):  1806-1813.  doi:10.11949/j.issn.0438-1157.20151614
    Abstract ( 99 )   PDF (5529KB) ( 224 )  
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    Subcooled degree is the direct drive potential of condensing phenomena happening and developing. The nucleation process of cascade passage sharply occurs in a narrow flow section. Water droplets distribution is affected by boundary layers and wakes. Due to the condensing parameters distribution steep and sensitive, high resolution second-order TVD scheme and time-marching technique were adopted in numerical algorithm. Using numerical algorithm, the condensing parameter distributions was calculated and compared with measured data to verify the accuracy of the numerical algorithm. Basic physical phenomena of non-equilibrium condensing flow and the influence of inlet subcooled degree on the homogenous nucleation were examined. Varying pattern of pressure, nucleation rate, droplets number, droplets radius and wetness were investigated. It was found that the inlet subcooled degree had a significant influence on non-equilibrium phase change in transonic condensing flow.

    Enhanced heat transfer mechanism of winglet vortex generator in helical channel with semicircular cross section
    LI Yaxia, ZHANG Teng, ZHANG Chunmei, ZHANG Li, WU Jianhua
    2016, 67(5):  1814-1821.  doi:10.11949/j.issn.0438-1157.20151623
    Abstract ( 83 )   PDF (1214KB) ( 116 )  
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    The purpose of this paper is to obtain the enhanced heat transfer characteristic of the winglet vortex generator (VG) in the helical channel with semicircular cross section. The shape and layout of the VG are concerned. CFD software is adopted to simulate the fluid flow and heat transfer characteristic in the smooth helical channel and that installed with four kinds of winglet vortex generator. The four styles of vortex generator are characterized as jxjs, jxjk, sjjs and sjjk VG, respectively. The simulated data coincide well with the experimental data. The results based on the current research show that after installing the vortex generator, the average ratio of Num to Nu0 is in the range of 1.044—1.074 where Num is the surface average Nusselt number of helical channel within the scope of ±180o away from the vortex generator and Nu0 is the corresponding value of smooth helical channel. However, the specific value between the flow resistance coefficient of helical channel with VG and the corresponding value of smooth channel, i.e. f/f0 is in the range of 1.105—1.188. The rectangular winglet VG is superior to the triangular winglet VG only in terms of heat transfer enhanced. Along with the flow direction, the convergent layout of VG is superior to the divergent layout for heat transferring. Based on the field synergy principle, the secondary flow field structure would be changed by the vortices shedding from the VG. Thus, the cooperativity of flow and temperature fields would be better and the heat transfer would be improved. For the helical channel with rectangular and triangular winglet VG, the compound secondary flow fields are four vortices and two large vortices, respectively, and the length of heat transfer effect is 10.47 and 12.56 times of winglet height, respectively.

    Characteristics of flow boiling heat transfer for R134a in pump-assisted separated heat pipe
    LI Xiaohua, SHAO Jie, LIU Ruijing, MA Tengfei, GUO Zhenjiang, TIAN Xiaoliang
    2016, 67(5):  1822-1829.  doi:10.11949/j.issn.0438-1157.20151713
    Abstract ( 84 )   PDF (1555KB) ( 247 )  
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    In order to address the complexity of the process of two-phase flow boiling in pump-assisted separated heat pipe and the poor experimental reproducibility, an experimental apparatus of pump-assisted separated heat pipe was built to study the pressure gradient and heat transfer coefficient of boiling heat transfer for R134a serving as a medium of heat transfer, which were compared with those in open literature. It showed that the integration of pressure gradient by Muller-Steinhagen-Heck correlation fits experimental result well with an error bar below ±10%. Moreover, at vapor quality above 0.1, Mohseni correlation predicts the experimental heat transfer coefficient with an error bar of ±10%, while at vapor quality below 0.1, it does with some error bars above 30%. For the purpose of minimizing the large error bars a modified correlation was built. Efforts of above correlation results were conducted as a reference standard for experimental study, numerical simulation and optimization design of heat pipe system.

    Effect of four components ratios on performance of auto-refrigerating cascade system
    RUI Shengjun, ZHANG Hua, DONG Bin, LIANG Kunfeng
    2016, 67(5):  1830-1836.  doi:10.11949/j.issn.0438-1157.20151155
    Abstract ( 112 )   PDF (490KB) ( 542 )  
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    An auto-refrigerating cascade cycle has some unique advantages for small refrigeration units, for which it has a wide range of operation temperatures from 77 K for nitrogen liquefaction to 230 K for conventional refrigeration. For the three-level auto-refrigenerating cascade system, effect of the components ratios of non-azeotropic mixture as a medium on the performances was investigated. Through the experimental comparisons of the performance of compressor and the cooling performance of evaporator, refrigerant mixtures of R600a, R23 and R14 with four ratios of 35/35/30, 35/30/35, 30/35/35 and 35/25/40 were designed, of which all the conditions of evaporator were approximate. The evaporation temperature for the ratio of 35/30/35 was lower than others. For this auto-refrigerating cascade system, its evaporator temperature can be as stable as down to 175 K under conditions of 60 W cooling load and 180 K of designed evaporation temperature. Based on the experimental study on the performances of the two compositions under different cooling loads, the highest COP values of 8.47% and 14.4% for the ratios of 35/30/35 and 35/35/30 were achieved, respectively.

    Large eddy simulation of gas turbulent deflagration in small-scale confined space
    WEN Xiaoping, YU Minggao, DENG Haoxin, CHEN Junjie, WANG Fahui, LIU Zhichao
    2016, 67(5):  1837-1843.  doi:10.11949/j.issn.0438-1157.20151219
    Abstract ( 94 )   PDF (4936KB) ( 264 )  
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    A 3D model of small-scale confined space with an inner size of 150 mm × 150 mm × 500 mm was set up. Based on the flame surface density model and the turbulent combustion model by Charlette et al., a large wddy simulation (LES) had been carried out on the process of gas deflagration flame-turbulence interaction with continuous obstacles at two sides of the chamber. All numerical results have been compared to experimental data. It showed that the LES is capable to predict the flame structure, position, speed, and overpressure in the process of gas deflagration, and the applicability of the LES and turbulent combustion model on gas deflagration was verified. In addition, the interaction between gas deflagration and turbulence and the relationship were described quantitatively by the Karlovitz number, and the transient flame regimes also identified. Under condition of continuous obstacles at double sides of the chamber, the gas turbulent deflagration flame experienced in the subsequent states of corrugated flamelets zone and thin reaction zone.

    Simplified analysis of heat transfer for vertical multi-boreholes ground heat exchangers
    YU Mingzhi, MA Tengteng, ZHANG Kai, HU Aijuan, CUI Ping, FANG Zhaohong
    2016, 67(5):  1844-1851.  doi:10.11949/j.issn.0438-1157.20150946
    Abstract ( 82 )   PDF (1077KB) ( 153 )  
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    Taking geometric symmetry and the approximately same periodic variation of the temperature field around partial buried pipes into account, simplified analysis of heat transfer for vertical multi-boreholes ground heat exchangers was carried out. On the basis of finite line heat source model, an example of non-seepage matrix layout of vertical multi-boreholes ground heat exchangers was selected to simplify the analysis of heat transfer. For the purpose of simplification on heat transfer analysis, representative buried pipe matrix (RBPM) was proposed in place of the original vertical multi-boreholes ground heat exchangers. Through the analysis on heat transfer of a single buried pipe and RBMP, it was considered that the heat transfer of RBPM can be determined according to the influencing radius of heat transfer of a single buried pipe under the same conditions of the geological conditions, geometry parameters, loads and operation conditions. Thermal conductivity of soil affects the scale of RBPM. Under the conditions in this article, the larger thermal conductivity of the soil is, the smaller scale of RBPM is.

    Influence of SDBS on start time and heat transfer performance of pulsating heat pipe
    CAI Jichi, WANG Ruixiang, XU Rongji, ZHANG Yihao, DING Siyuan
    2016, 67(5):  1852-1857.  doi:10.11949/j.issn.0438-1157.20151160
    Abstract ( 92 )   PDF (769KB) ( 159 )  
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    Surface tension is one of the important factors that influences the behaviors of the working fluid bubbles, such as generation, pulsation split and merge. Furthermore, the heat transfer performance of pulsating heat pipe (PHP) is affected. Three concentration solutions 0.001%, 0.005% and 0.009% were configured using sodium dodecyl benzene sulfonate (SDBS) as solute and deionized water as base fluid. The surface tension of water was decreased by 42.2% after addition of 0.005% SDBS, while little change of the specific heat, density and viscosity. Both the start-up and heat transfer performance of PHP were test with the concentration solutions under different heating power input. The experimental results indicated that SDBS can reduce the start-up time of the pulsating heat pipe. Start-up time of 0.001% solution was the shortest with the heating power input no more than 90 W. Differently, the addition of SDBS has little effect on the start-up time under high heating power input. At steady working station, the heat transfer performance of PHP was improved by adding SDBS.

    Relationship between longitudinal vortex intensity and heat transfer intensity of flat tube heat exchanger
    SONG Kewei, LIU Song, WANG Liangbi
    2016, 67(5):  1858-1867.  doi:10.11949/j.issn.0438-1157.20151231
    Abstract ( 109 )   PDF (2107KB) ( 188 )  
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    The longitudinal vortices can potentially enhance heat transfer with small pressure loss penalty. Vortex generators (VGs) which can generate longitudinal vortices are widely used in fin-and-tube heat exchangers for heat transfer enhancement. But for a long time, researches are carried out focusing on the effect of the shape and parameters of VGs on heat transfer and the relationship between the longitudinal vortices intensity and heat transfer intensity is analyzed qualitatively. The quantitative relationship between the longitudinal vortices intensity and heat transfer intensity is seldom reported. Longitudinal vortex is a typical secondary flow, and thus the longitudinal vortex intensity can be defined using the secondary flow intensity parameter. In this paper, the numerical models of flat tube bank fin heat exchanger with VGs mounted on the fin surfaces are studied for different fin and VGs parameters. The longitudinal vortices intensity is quantitatively defined using the nondimensional secondary flow intensity parameter Se. The relationship between the longitudinal vortices intensity and the heat transfer intensity and that between the increment values of Se and Nu caused by the longitudinal vortices are quantitatively studied. The results show that there is no corresponding relationships neither between Nu and Re, nor between Se and Re. Similarly, no linear relationship exists between the friction factor f and the values of Re and Se. But the corresponding relationship exists not only between Se and Nu but also ΔSe and ΔNu. The longitudinal vortices intensity determines the heat transfer intensity in the flat tube fin heat exchanger.

    Expansion and detachment characteristics of bubble at downward nozzle of vertical flat pipe
    WU Xuan, JIAO Jingjing, LIANG Panlong, JIN Guang, WU Wenfei
    2016, 67(5):  1868-1877.  doi:10.11949/j.issn.0438-1157.20151478
    Abstract ( 130 )   PDF (5135KB) ( 175 )  
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    Gas bubbles in liquid influence efficiency of mass and heat transfer. Much efforts on the observation of expansion and detachment of bubble at upward nozzle have been conducted, while that of downward nozzle is rarely known. In this article, the expansion and detachment of bubble at the downward nozzle of vertical flat pipe was observed by a high speed camera. Effect of the nozzle diameter and average gas velocity on bubble size and time of formation was investigated. The bubble age, k and the diameter ratio of long axis to short axis, L describe bubble position and bubble shape, respectively. It showed that three kinds of mechanism of intermittent formation, intermittent formation with suction and continued formation exist in bubble formation. With the variation of detachment diameter of bubble as a function of average gas velocity, a critical point representing the evolution of bubble detachment exists. The expansion and detachment of bubble along with average gas velocity, follow two types of single bubble formation and coalescence formation. The suction phenomenon occurred at 3.1 m·s-1 of average gas velocity, of which kmax is minimized. In the detachment stage, a critical point of detachment time exists in the evolution of L as a function of time, namely, L allocates around 2.0 with mostly ellipsoidal bubble before the critical point, however, L increases significantly with the formation of flat ellipsoidal bubble after the critical point.

    Particle rotation characteristics in impinging streams
    DU Min, CHEN Wei, WANG Zhuliang, GONG Jun, WANG Hongyu
    2016, 67(5):  1878-1883.  doi:10.11949/j.issn.0438-1157.20151655
    Abstract ( 98 )   PDF (1376KB) ( 217 )  
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    An experimental device of gas-solid impinging streams was built up to study particle rotation characteristics. High-speed video camera system was used to observe particle motion in area of 0.15 m × 0.08 m. The influence factors of particle rotation were studied by using this experimental device with single injection or double injections. The particle rotation characteristics was obtained by analyzing those research data. The results showed that the particles always rotated when moving along the gas-solid impinging streams. The influence of gas on particle rotation was relatively small, and therefore it can be ignored. The average rotation speed of particles with smaller diameter was higher than that with greater diameter under same experimental conditions. Those particles with relatively higher velocity before collision were inclined to have a higher rotational speed after collision. The average difference between particle rotation speeds before and after collision can reach 280 r·s-1 at gas velocity 25 m·s-1 and diameter of alumina cement 0.003 m. The direction of particle motion has little influence on the particle rotation speed during collision.

    Synthesis of 2-ethyl-2-hexenal via n-butanal self-condensation catalyzed by La-Al2O3
    LIU Xiaohong, WANG Yi, AN Hualiang, ZHAO Xinqiang, WANG Yanji
    2016, 67(5):  1884-1891.  doi:10.11949/j.issn.0438-1157.20151260
    Abstract ( 121 )   PDF (628KB) ( 152 )  
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    2-Ethylhexanol is a kind of important plasticizer alcohols. n-Butanal self-condensation to 2-ethyl-2-hexenal is one of the important processes for industrial production of 2-ethylhexanol. In order to overcome the shortcomings such as equipment corrosion, environmental pollution and high production cost in the present industrial n-butanal self-condensation reaction using alkali aqueous catalyst, the La-modified γ-Al2O3 catalyst (La-Al2O3) was adopted to catalyze n-butanal self-condensation reaction. Firstly, the influence of different preparation methods and conditions on the La-Al2O3 catalytic activity was studied. The results showed that the catalytic activity of La-Al2O3 prepared by colloidal chemical method and calcined at 700℃ for 4 h was better. The existing acidic centers and basic centers matching with each other were the key to present better catalytic activity. The influence of reaction conditions on n-butanal self-condensation reaction was studied using the La-Al2O3 catalyst. The suitable reaction conditions were obtained as follows: mass ratio of catalyst to n-butanal 0.15:1, reaction temperature of 180℃ and reaction time of 8 h. Under the above conditions, the conversion of n-butanal was 90.6% and the selectivity of 2-ethyl-2-hexenal was 91.7%. La-Al2O3 could be reused for 4 recycles without losing its activity significantly. In addition, the by-products existing in the reaction system were identified by GC-MS analysis and then a possible reaction network for n-butanal self-condensation to 2-ethyl-2-hexenal catalyzed by La-Al2O3 was established.

    Promoters modified FeOOH and their catalytic performances for direct coal liquefaction
    XIE Jing, LU Hanfeng, CHEN Yinfei, GAO Shansong, WANG Hongxue
    2016, 67(5):  1892-1899.  doi:10.11949/j.issn.0438-1157.20151604
    Abstract ( 99 )   PDF (8484KB) ( 168 )  
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    Modified FeOOH catalysts were prepared by a co-precipitation method using Si, Al, La, Ca, Mg, Zr, Cu, Ni and Co as promoters, respectively. The effects on microstructures, crystalline phase and morphology of the catalysts were characterized by BET, XRD and SEM. Their catalytic performances for the direct liquefaction of Shendong coal were evaluated in a 0.5 L stirring autoclave. The results showed that these promoters (Si, Al, Ca, Zr, Ni and Co) could improve the dispersion of the catalysts and surface area, and then improve the catalytic performances for direct coal liquefaction. Increasing by 0.7%—2.7% oil yield over the unmodified the catalyst could be obtained. However, Mg showed no effect on catalytic ability, while Cu and La reduced the Oil yield. The result indicated that Si, Al, Ca and Zr as the structure promoters could significantly improve the texture properties of catalysts, resulting in an increase of γ-FeOOH crystalline phase with small size which was beneficial to form active phase (Fe1-xS). Co and Ni as the electronic promoters could activate H2 preferentially to promote liquefaction, leading to the rising in oil yield.

    High selective synthesis of ortho isomer of bisphenol F catalyzed by Zr-SBA-15
    TAN Ying, LI Yongfei, WEI Yuanfeng, YAN Jiaqi, WU Zhimin, PAN Langsheng, LIU Yuejin
    2016, 67(5):  1900-1906.  doi:10.11949/j.issn.0438-1157.20151257
    Abstract ( 97 )   PDF (620KB) ( 258 )  
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    A molecular sieve catalyst Zr-SBA-15 was synthesized by the hydrothermal one-step method using P123, TEOS and ZrONO3·xH2O as template agent, silicon and zirconium sources, respectively. The Zr-SBA-15 catalyst was characterized by XRD, BET, ICP, pyridine-FTIR and NH3-TPD, respectively, and used to mainly synthesize the ortho isomer of bisphenol F from phenol and formaldehyde. The results showed that the pore diameter of the prepared Zr-SBA-15 catalyst was about 6.6 nm and the distribution of pore diameter was uniform. After Zr incorporated into SBA-15, it had a high proportion of Lewis acid sites favouring the forming of the ortho isomer of bisphenol F with high catalytic activity. When the molar ratio of Si/Zr was 20, the Zr-SBA-15 catalyst exhibited the best catalytic activity with 83.5% of yield and 92.5% of ortho isomer of bisphenol F. The optimized reaction conditions were obtained as the phenol/formaldehyde molar ratio 30, the catalyst/formaldehyde mass ratio 1, reaction temperature 90℃ and reaction time 240 min. The reaction mechanism for high selective synthesis of the ortho isomer of bisphenol F was also proposed.

    Synthesis and performance of heterogeneous catalyst of immobilized acidic ionic liquid on SBA-15 for esterification
    HU Jingjing, ZHAO Dishun, HU Tiantian, LI Jingjing, ZHAI Jianhua
    2016, 67(5):  1907-1914.  doi:10.11949/j.issn.0438-1157.20151557
    Abstract ( 123 )   PDF (720KB) ( 188 )  
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    To decrease the usage of ionic liquid and facilitate the separation of catalyst from the product, a novel Brønsted acidic ionic liquid catalyst of 1-(3-sulfopropyl)caprolactam hydrogen sulfate ([C3SO3HCP]HSO4) supported on SBA-15 was prepared through covalent bond grafting method. In order to achieve structural information and stability of catalysts, the samples were characterized by FT-IR, TG, XRD, BET and TEM techniques. The catalytic activities of the immobilized ionic liquid for the esterification of succinic anhydride with ethanol were investigated. It showed that [C3SO3HCP]HSO4 has been successfully immobilized onto the SBA-15 with relatively good thermal stability and catalytic activity, which overcomes the drawbacks of low activity of heterogeneous catalyst, and difficult separation of homogeneous catalyst from the reaction system. Under the optimized conditions of 5%(mass) of catalyst dosage, n(C4H4O3):n(C2H5OH)=1:3, 80℃ of reaction temperature, 4 h of reaction time, and 30%(mass) of water carrying agent dosage, the yield of diethyl succinate was up to 93.7%. The SBA-15 immobilized ionic liquids remained satisfactory catalytic activity for the synthesis of diethyl succinate after 8 cycles. Moreover, the IL/SBA-15 exhibited relatively high yield of diethyl succinate for a series of esterification and the product could be separated easily from the reaction system.

    Visible near-infrared amino phthalocyanine-titanium dioxide photocatalyst: preparation and performance
    XU Yanming, ZHAO Ming, LI Jian, REN Qiang, WANG Chenyi
    2016, 67(5):  1915-1921.  doi:10.11949/j.issn.0438-1157.20151401
    Abstract ( 123 )   PDF (679KB) ( 312 )  
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    An α-TDMACuPc-TiO2 photocatalyst was prepared through Sol-Gel method using 3,3',3",3"'-tetra-dimethylamino copper(Ⅱ) phthalocyanine (α-TDMACuPc) of a soluble amino phthalocyanine as a sensitizer. The photocatalyst was characterized by ultraviolet-visible spectroscopy (UV-Vis) and X-ray diffraction (XRD). Its photocatalytic performance for the degradation of methyl violet was evaluated. It showed that α-TDMACuPc sensitizer exhibited strong absorption in near-infrared region, and the absorption spectrum of sensitized TiO2 could be extended to visible near-infrared light region. Besides, the sensitized TiO2 features rutile structure. Its sensitization by α-TDMACuPc significantly improved the photocatalytic activity of TiO2 in visible near-infrared light region. The α-TDMACuPc-TiO2 photocatalyst with 1%(mass) α-TDMACuPc exhibited the highest catalytic activity as well as relatively good stability.

    Triple region model for calculating fractional efficiency of combined system of circulation pre stripper and vortex quick separator
    HUANG Shiping, E Chenglin, WANG Zijian, LU Chunxi
    2016, 67(5):  1922-1930.  doi:10.11949/j.issn.0438-1157.20151464
    Abstract ( 77 )   PDF (713KB) ( 146 )  
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    The gas flow field and the fractional efficiency of a novel combined system of circulation pre stripper & vortex quick separator (CVQS) were investigated via a large-scale cold model. The results showed that the separation efficiency of particles under 7 μm almost unchanged with increasing ejection gas speed, while getting smaller when the particle size was between 7 μm to 20 μm, and higher as the particle size is beyond 20 μm. On the basis of above investigations, the gas-solid separation mechanism of CVQS was talked over, and a triple region model used for analyzing the fractional efficiency of CVQS was proposed. The calculated results showed that this model was in good agreement with experimental data within the larger particle size distribution (beyond 20 μm) and the maximum relative deviation was under 6.1%. For the particle under 20 μm, there was an obvious difference between experimental and model values, whose relative deviation was within 45.7% and 80.5%, respectively. Therefore, the triple region model had important reference value in CVQS engineering design for separating particles beyond 20 μm.

    Adsorption and recovery of low concentration coal-bed methane by zeolite ZSM-5
    LIU Haiqing, WU Yijiang, YANG Ying, YANG Lin, LI Ping, YU Jianguo
    2016, 67(5):  1931-1941.  doi:10.11949/j.issn.0438-1157.20151684
    Abstract ( 109 )   PDF (1333KB) ( 293 )  
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    As a high-silica hydrophobic material, zeolite ZSM-5 was used for the adsorption and recovery of low concentration coal-bed methane. Theoretical and experimental studies were conducted on adsorption equilibrium, adsorption kinetics and vacuum pressure swing adsorption (VPSA). Single and binary competitive adsorption equilibrium experimental data of CH4/N2 on zeolite ZSM-5 were measured by gravimetric method and breakthrough-curve method. The multi-site Langmuir model was used to fit the experimental data. Microporous diffusion coefficients were calculated based on the experimental data of diluted breakthrough curves and simulated results of an isothermic mathematical bi-disperse model without momentum loss. Competitive breakthrough curves of CH4 and N2 on zeolite ZSM-5 were predicted by fixed bed adsorption models with mass, momentum and energy transfer. Effects of CH4 concentration in feed, feed flow rate, feed time and purge/feed flow rate ratio on separation performances of ZSM-5 packed single column four-step VPSA process were investigated. It showed that ZSM-5 zeolite exhibited a relatively good selectivity for CH4 and the diffusion in micropores was the rate determining step for both CH4 and N2 adsorption. By the process of VPSA, CH4 purity can be concentrated from 20% to 31%~41% and the recovery can be up to 93%~98%.

    Effects of temperature on adsorption mechanism and adsorption selectivity of C3H6 and C3H8 on MOF-74(Ni)
    LIU Jiang, WU Yufang, XU Feng, XIAO Jing, XIA Qibin, LI Zhong
    2016, 67(5):  1942-1948.  doi:10.11949/j.issn.0438-1157.20151519
    Abstract ( 236 )   PDF (633KB) ( 910 )  
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    MOF-74(Ni) was synthesized by solvothermal synthesis method and then characterized by PXRD and pore size analysis. Isotherms of C3H6 and C3H8 on the synthesized MOF-74(Ni) were measured at different temperatures. The temperature programmed desorption experiments were conducted to estimate the desorption activation energies of C3H6 and C3H8 on the MOF-74(Ni). IAST theory was applied to predict the adsorption selectivity of C3H6/C3H8 mixture. The effects of temperature on adsorption mechanism and adsorption selectivity were also discussed. Results showed that the as-synthesized MOF-74(Ni) had BET surfaces of 1306 m2·g-1, and its C3H6 adsorption capacity was up to 7.4 mmol·g-1 at 298 K. With rising temperature, the adsorption capacity of C3H8 on MIL-74(Ni) decreased sharply, while that of C3H6 decreased slightly, resulting in improvement of C3H6/C3H8 adsorption selectivity of MOF-74(Ni). It could be attributed to p-complexation bonding between C3H6 and MOF-74(Ni), which was stronger than the interaction of C3H8 with MOF-74(Ni). TPD results indicated that the desorption activation energy of C3H6 on MOF-74(Ni) was higher than that of C3H8, which were 68.92 kJ·mol-1 and 50.80 kJ·mol-1, respectively.

    Adsorption behavior of magnetic triethylene tetramine-graphene oxide nanocomposite for Cu2+
    CHEN Fangni, SUN Xiaojun, WEI Jinzhi, LIU Xianbin, HU Qin
    2016, 67(5):  1949-1956.  doi:10.11949/j.issn.0438-1157.20151130
    Abstract ( 104 )   PDF (5069KB) ( 252 )  
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    A novel composite adsorbent of magnetic triethylene tetramine graphene oxide (M-T-GO) was firstly prepared by isothermal stirring and hydrothermal method to improve adsorption ability and separation efficiency of graphene oxide (GO). M-T-GO was characterized by Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The pH, adsorption kinetics, isotherms and thermodynamics of Cu2+ on M-T-GO were studied, indicating that the adsorptions kinetic was well fitted by pseudo-second-order model and the equilibrium adsorption was well described with Langmuir model. The saturated adsorption capacity of Cu2+ was about 245.09 mg·g-1 on M-T-GO. M-T-GO could make separation of the adsorbents easy in the foreign magnetic field and possess good performance of regeneration. The adsorption process of Cu2+ was spontaneous and endothermic by the calculated thermodynamic parameters. X-ray photoelectron spectroscopy (XPS) spectra suggested that Cu2+ was adsorbed on M-T-GO mainly through the chelation and electrostatic attraction.

    Fabrication of silica-decorated membranes with superhydrophilicity and evaluation of their performances in oil/water emulsion separation
    ZHENG Ximing, FAN Rongyu, XIAO Qirui, KONG Xianglong
    2016, 67(5):  1957-1964.  doi:10.11949/j.issn.0438-1157.20151422
    Abstract ( 137 )   PDF (4743KB) ( 362 )  
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    Using silica sol and dopamine as modifiers, SiO2 modified layers were fabricated on the microporous polypropylene membrane (MPPM) surfaces by a one-step reaction. The resulted membranes were characterized with Fourier transform infrared spectroscopy (FTIR), environmental scanning electron microscopy (ESEM) and energy dispersive X-ray spectroscopy (EDX). The results confirmed that SiO2 particle was dispersed uniformly on the MPPM surface. The experimental results of water/oil contact angle and water flux indicated that the modified membranes had superhydrophilic and underwater superoleophobicity surface, and showed excellent water permeability with high pure water flux [up to (5100±500) L·m-2·h-1 under 0.1 MPa]. The separation abilities of the modified membranes for oil/water emulsion were also investigated. It was found that the modified membranes could separate oil/water emulsion effectively with a highest water flux of 2830 L·m-2·h-1 and oil rejection ratio of 99.8% under 0.05 MPa. Moreover, oil rejection ratio of the modified membranes could retain above 99% even under 0.15 MPa, and the oil attached to the membrane surfaces could be easily removed by water. The silica-decorated membranes enable an efficient and energy-saving separation for oil/water emulsion, and thus shows attractive potential for practical oil/water emulsion separation.

    Heat pipe-based experimental study on water separation process in vacuum evaporator
    GAO Wenzhong, LI Changsong, XU Changda, LIU Ting
    2016, 67(5):  1965-1972.  doi:10.11949/j.issn.0438-1157.20150920
    Abstract ( 135 )   PDF (3400KB) ( 236 )  
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    Based on the remarkable heat transfer performance of heat pipe (HP) and great specific surface area of small diameter droplets, HP and spray technologies are used in a novel single stage vacuum evaporator. And man-made seawater with 3% saltness is tested. Parameters affecting the performance such as temperature of cold source and heat source, spray temperature and spray flow are investigated. The result shows that the maximum heat flux of evaporator bland plate is 32 W·cm-2. HPs absorb energy from low grade heat source between 40 to 80℃, and then transfer the energy to the droplets already flashed to keep or even increase the degree of superheat while evaporate. Thus, this method can significantly improve the water separation rate (quality of condensed water/quality of dilute solution ×100%). The initial superheat degree is replaced by temperature of cold source and heat source as the major factor on separating effect. The control of separation rate can be realized through adjusting the parameters. Therefore, this method has important implications for effective utilization of lower grade heat source, gaining brine and promoting the fresh water production unit volume and adaptability to variable load in desalination project.

    Fault detection method based on non-negative matrix factorization for multimode processes
    ZHU Honglin, WANG Fan, SHI Hongbo, TAN Shuai
    2016, 67(5):  1973-1981.  doi:10.11949/j.issn.0438-1157.20151392
    Abstract ( 70 )   PDF (620KB) ( 176 )  
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    The traditional multivariate statistical fault detection methods are designed for single operating conditions and may produce erroneous conclusions if they are used for the multi-mode process monitoring. A novel multi-mode process monitoring approach based on non-negative matrix factorization (NMF) is proposed in this paper. First, the training set of data is clustered by the standard NMF algorithm and the multi-mode data are divided into each mode. Then, the sparseness orthogonal NMF (SONMF) algorithm is used to model every mode and the monitoring statistics are constructed to perform fault detection. The proposed method is applied to a numerical example and the TE process. The simulation results show that this method can effectively detect multi-mode process failure.

    Modeling of cracking furnace yields with PSO-LS-SVM based on operating condition classification by transfer learning
    LIU Jia, SHAO Cheng, ZHU Li
    2016, 67(5):  1982-1988.  doi:10.11949/j.issn.0438-1157.20151745
    Abstract ( 88 )   PDF (545KB) ( 171 )  
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    The prediction of ethylene cracking furnace yields on line is significant in industrial production for advanced control and energy efficiency. Due to the great differences between different operating conditions, single condition and modeling may not satisfy the requirement of practical process. Considering the similarity of cracking furnace and the reduction of acquisition cost, the history data are utilized assisting transfer learning to improve the accuracy of operating condition classification. Least squares support vector machines (LS-SVM) is employed in modeling cracking furnace yields in different operating conditions, which enjoy stronger generalization ability and faster convergence speed compared with standard SVM. The accuracy is further improved by optimizing parameters of LS-SVM with particle swarm optimization (PSO), and thus establishing different operating condition models for yields prediction. The simulations and operating condition classifications are given based on the real industrial data to demonstrate that the operating condition classification is more reasonable. The prediction of LS-SVM optimized with PSO is more accuracy and behaves good trend tracking performance.

    Subset multiway principal component analysis monitoring for batch process based on affinity propagation clustering
    HU Yongbing, GAO Xuejin, LI Yafen, QI Yongsheng, WANG Pu
    2016, 67(5):  1989-1997.  doi:10.11949/j.issn.0438-1157.20151454
    Abstract ( 68 )   PDF (1027KB) ( 138 )  
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    For the multiphase property inherent in the batch process, and in order to overcome the serious deficiency that the traditional stage partition method divided the sampling points into several categories strictly according to the sampling time sequence and cannot make it look for the clustering center with the most similar data characteristics, a novel subset-MPCA method based on affinity propagation (AP) clustering is proposed. Using a new idea of random order clustering, this method disrupts the order of the time slice and AP is used to cluster with the random order. Thus, each data point can break the restriction of the time sequence and find the clustering center which has the most similar data characteristics with it, obtaining clustering subset and establishing the precise model. For online monitoring, information transmission is introduced to determine the stage attribution of real time sampling points to solve the problem of optimal model selection for unequal length batch. Experiments on penicillin simulation data show that this method can effectively reduce the leaking alarms and nuisance alarms than the traditional method, having more reliable monitoring performance.

    Electrochemical reduction of nitrobenzene in binary ionic liquid of OMImBF4/HMImPF6
    MAO Xinbiao, HE Fengqiang, ZHANG Yinxu, CHEN Song, LIU Ying, MA Chun'an
    2016, 67(5):  1998-2004.  doi:10.11949/j.issn.0438-1157.20151486
    Abstract ( 86 )   PDF (673KB) ( 114 )  
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    A mixture of ionic liquids (ILs), OMImBF4 and HMImPF6 was prepared, for which its conductivity and infrared spectroscopy (IR) were measured in comparison with those of components. In the binary IL system with varied volume ratios of OMImBF4/HMImPF6, techniques of cyclic voltammetry (CV), chronoamperometry (CA), constant-potential electrolysis, in-situ Flourier transform infrared spectroscopy (in-situ FTIRS), GC-MS and GC were employed to investigate electrochemical reduction of nitrobenzene. It showed that, the conductivity of OMImBF4/HMImPF6 decreased with the concentration of HMImPF6 component, and IR bands of [BF4]- and [PF6]- in the IL mixture obviously changed from each single component. The OMImBF4/HMImPF6 IL system with 3:1 of volume ratio exhibited a higher current density and a more positive potential for the reduction of nitrobenzene, and also the selectivity and yield of main product azobenzene than single component ILs. The rate-determining step in the electrochemical reduction of nitrobenzene is diffusion, of which diffusion coefficient is 2.024×10-7 cm2·s-1.

    Effects of waviness and taper on cavitation characteristics of liquid lubricated mechanical seals
    LI Zhentao, HAO Muming, YANG Wenjing, HAN Jie, REN Baojie
    2016, 67(5):  2005-2014.  doi:10.11949/j.issn.0438-1157.20151733
    Abstract ( 133 )   PDF (899KB) ( 141 )  
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    In order to further probe into the influence factors of cavitation start and evolution, the mathematical model of liquid film lubricated mechanical seals considering the micro circumferential waviness and radial taper was established based on the mass-conservative cavitation model. Liquid film governing equation was discretized by the finite control volume method and was solved by the Gauss-Seidel relaxation iterative algorithm. The effects of different waviness amplitudes, waviness numbers and tapers on the cavitation characteristics were analyzed. The results indicated that the start and evolution of the cavitation were affacted by the combined action of the hydrodynamic lubrication effect produced by the circumferential waviness and the hydrostatic lubrication effect which was greatly influenced by radial taper. To a large extent, changing of the cavitation area along the circumferential direction was influenced by the waviness, while that along the radial direction depended on the taper. The rupture position of liquid was located where film thickness diverged in the depression region at the start stage of cavitation, while the subsequent rupture direction remained unchanged at the evolution stage of cavitation. The cavitation rate was dramatically accelerated at the situations of dimensionless waviness amplitude not beyond 0.5 and waviness number greater than or equal 8, or dimensionless negative taper value greater than 0.5, which promoted the occurrence of cavitation. But under the same waviness amplitude and waviness number less than 8 or the taper tending to be positive, the cavitation rate was retarded, which effectively inhibited the occurrence of cavitation.

    Kinetic modelling of porcine insulin precursor (PIP) expressed by multi-copy recombinant Pichia pastoris
    CHEN Li, WANG Yue, GUO Meijin, CHU Ju, ZHUANG Yingping
    2016, 67(5):  2015-2021.  doi:10.11949/j.issn.0438-1157.20151432
    Abstract ( 113 )   PDF (598KB) ( 263 )  
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    Kinetic modelling of recombinant Pichia pastoris harboring multiple porcine insulin precursor (PIP) gene dosages was studied when the cells were grown in the fed-batch culture. The key parameters of this kinetics were estimated, including specific cell growth rate (h-1), PIP production rate (g·g-1·h-1) and substrate consumption rate (g·g-1·h-1) with nonlinear curve fit by Origin8.0. The results showed that both growth-associated production coefficient ( ) and growth-associated metabolism coefficient (k1) increased with increasing copy numbers. The expression level of PIP reached the highest at the copy number of 12. These results suggested that rapid growth and lower metabolic burden of a high copy number effectively improved the production rate of target proteins. Furthermore, the predicted values based on the established kinetic model were in good agreement with the experimental data, indicating that the kinetic model could be used to describe recombinant PIP production process in fed-batch fermentation mode.

    Electrochemical continuous separation of oxygen from air (Ⅰ): Optimum of single cell performances
    ZHU Xiaobing, ZHANG Jianhui, LI Xiaosong, LIU Jinglin, LIU Jianhao, JIN Can
    2016, 67(5):  2022-2032.  doi:10.11949/j.issn.0438-1157.20151502
    Abstract ( 108 )   PDF (813KB) ( 361 )  
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    With rapid development of industrial processes, in particular more recently influenced by “Haze”, air quality draws more and more attentions. A refill of oxygen in air is one of crucial solutions to improve air quality. In contrast to conventional technologies for oxygen production (i.e. physical separation of air, chemical reactions, water electrolysis), the innovative technology of electrochemical continuous separation of oxygen from air features separation of pure oxygen from air, high efficiency, continuous operation, environment friendly, silent operation, ease of scale up and applicability to indoor or outdoor fields. This technology involves two crucial components of polymer electrolyte fuel cells and solid polymer electrolyte water electrolysis (abbreviated as fuel cell and electrolyzer). In this article, the effect of operation conditions on single cell performance such as operation temperature, reactant gases utilization ratios, relative humidity and pressure, etc. for fuel cell was investigated, as well as the ways of water supply (at anode and/or cathode), water flow rate and operation temperature, etc. for electrolyzer. In terms of fuel cell, the polarization curve was measured, the electrochemical impedance spectra were conducted and the ionic conductivity and activation energy of Nafion® membrane were calculated. Polarization curve was fitted to obtain intrinsic parameters including Tafel slope, exchange current density of oxygen reduction reaction (i0) and m, n, related to mass transfer etc. It showed that the optimum of fuel cell was under conditions of ambient pressure, 60℃ of operation temperature, 0.42 W·cm-2 of peak power density, 77 mohm·cm2 of cell areal resistance (membrane) and 41.4 mS·cm-1 of ionic conductivity. The Tafel slope slightly varied with temperature, ca. 120 mV·dec-1, but was influenced by the relative humidity. The relative humidity remarkably affected the fuel cell performances. In electrolyzer, the optimum was under conditions of 65℃ of operation temperature, 1.08 ohm·cm2 of cell areal resistance and 11.7 mS·cm-1 of ionic conductivity. The effect of water flow rate on performance was negligible. The ways of water supply follow an order of both anode and cathode≈anode>cathode. Under above conditions, activation energies of Nafion®211 and Nafion®115 membranes were calculated as 3.75 and 4.61 kJ·mol-1, respectively. Based on the optimum of single cell performances of fuel cell and electrolyzer, in this article, the preliminary experimental data were provided for the subsequent implementation of scale up of cell stack system for oxygen production.

    Selective inhibition of methanogens using 2-bromoethanesulfonate for improvement of acetate production from CO2 in bioelectrochemical systems
    QI Yujiao, BRIDIER Arnaud, DESMOND LE QUEMENER Elie, LÜ Fan, HE Pinjing, BOUCHEZ Théodore
    2016, 67(5):  2033-2040.  doi:10.11949/j.issn.0438-1157.20151517
    Abstract ( 132 )   PDF (709KB) ( 213 )  
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    In this study, the specific reduction of CO2 to acetate in presence of methanogenesis inhibitor 2-bromoethanesulfonate (BES) was studied in a bio-electrochemical system (BES) via a two stage experimental design. During first stage using untreated mixed anaerobic consortia, the methanogenesis was dominated and the CO2 reduction yielded methane at the maximum rate of 0.95 mmol·L-1·d-1 at nearly 55.0% coulombic recovery. Sequences belonging to the family Methanobacteriaceae were dominant at the cathodic electrode. During second stage, BES addition selectively suppressed the growth of methanogens, which resulted in a shift of the dominant activity to acetogenesis with the maximum production rate of 2.22 mmol·L-1·d-1 with a recovery of 67.3% of electrons in acetate and hydrogen after two duplicates. The main populations were Rhodocyclaceae (15.1%), Clostridiaceae (11.9%), Comamonadaceae (11.1%) and Sphingobacteriales (11.0%). This study highlighted the importance of inhibition of methanogenesis to manoeuvre microbial structures, which decided the final product profiles during a microbial electro synthesis operation.

    Simultaneous removal of SO2 and NOx by combination of ozone oxidation and Na2S2O3 solution spray
    YANG Ye, XU Chaoqun, ZHU Yanqun, LIN Fawei, MA Qiang, WANG Zhihua, CEN Kefa
    2016, 67(5):  2041-2047.  doi:10.11949/j.issn.0438-1157.20151536
    Abstract ( 289 )   PDF (535KB) ( 559 )  
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    Ozone oxidation and Na2S2O3 solution spray was combined to remove SO2 and NOx simultaneously. This coupling was studied experimentally. The results show that: SO2 and NOx can be eliminated simultaneously; at O3/NO mole ratio 1.1—1.2, the NOx removal efficiency increases with increasing concentration of Na2S2O3; existence of SO2 can facilitate removal of NOx; the NOx removal efficiency reaches 70% with low emission of SO2 at Na2S2O3 concentration 2.0% and at SO2 gas concentration 1030 mg·m-3. Furthermore, the NOx removal efficiency is enhanced with the pH of solution from 2.5 to 9, and reaches 75% at pH 9. The result of 3 hours running experiment indicates that NOx and SO2 can be removed efficiently and simultaneously and the stable and continuous operation is possible, because sodium thiosulfate can facilitate removal of NOx and the NOx is dominantly converted into NO2-. This process could be an efficient approach for eliminating SO2 and NOx simultaneously and could have potential industrial application.

    Kinetic modelling of total phosphorus removal in landscape type and vegetable type horizontal subsurface-flow constructed wetlands
    YIN Zhiping, WU Yifeng, LÜ Xiwu
    2016, 67(5):  2048-2055.  doi:10.11949/j.issn.0438-1157.20151445
    Abstract ( 98 )   PDF (647KB) ( 245 )  
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    The studies on total phosphorus (TP) removal in landscape type and vegetable type horizontal subsurface flow wetlands were conducted. The raw water was domestic sewage which has been treated by biochemical treatment processes. The TP removal efficiency of different wetland units were compared and analysed. To optimize the design of wetlands, the first order reaction kinetics model and the Monod model were used to simulate the TP removal results and their accuracy were compared. Meanwhile, the relationship between water temperature, hydraulic loading rate (q) and the reaction coefficients were discussed. The results showed that in landscape type wetlands, the order of TP removal capacity was canna unit >thalia dealbata unit >iris tectorum unit, while it was water spinach unit >zizania unit >tomato unit in vegetable type wetland units, which was attributed to the biomass difference of different plants. The comparative evaluation between the first order kinetics model (ME: 0.53—0.72) and the Monod model (ME: 0.76—0.86) showed that the Monod model had higher accuracy in predicting the TP removal results. Decreased values of areal removal efficiency of TP were observed at lower water temperature. The Kmax of canna (θ=1.006), thalia dealbata (θ=1.008) and water spinach units (θ=1.006) were insensitive to the change of water temperature. The water temperature had a great influence on TP removal efficiency of iris tectorum (θ=1.015) and zizania (θ=1.014) units. The increased values of Kmax20 were observed at higher q values. The power equations (R2: 0.657; 0.805) can well reflected the relationship between Kmax20 and q. The constructed Monod model, which had considered the influence of water temperature and q on Kmax, gave a certain accuracy in predicting TP removal of experimental wetlands.

    Synchronously degradation of biogas slurry and triphenyltin chloride in microbial fuel cell
    GU Dongyan, JIA Honghua, WU Yuandong, ZHOU Jun, WU Xiayuan, ZHENG Tao, YONG Xiaoyu
    2016, 67(5):  2056-2063.  doi:10.11949/j.issn.0438-1157.20151527
    Abstract ( 129 )   PDF (517KB) ( 178 )  
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    As a novel electrochemical apparatus for synchronous electricity generation and decontamination, microbial fuel cell (MFC) provides a way to effectively deal with the refractory pollutant. A new method of electricity production by anodic biogas slurry coupling with cathodic triphenyltin chloride degradation was proposed based on the cathodic “Fenton” reaction in a typical dual-chamber MFC. The results showed that the maximum voltage was 50.32% higher and the stable time of the voltage was 2 times longer after biofilms domestication. In the end of the operation, the removal efficiency of COD, Total N and Total P of the biogas slurry were 85.35%±1.53%, 59.20%±5.24% and 44.98%±3.57%, respectively. Besides, the triphenyltin chloride (TPTC) degradation efficiency decreased with increasing initial concentration. In addition, when 100 μmol·L-1 TPTC was added to the cathodic chamber, the highest output voltage and the maximum power density of the MFC arrived at 280.2 mV and 145.62 mW·m-2, respectively. TPTC was removed after 14 d with the degradation of 91.88% and a rate of about 0.273 μmol·L-1·h-1. This study provided the foundational supports for simultaneously decomposing anodic organic effluent and cathodic organic pollution by MFC.

    Ammonia escape and its prevention in CO2 absorption process using ammonia solution
    MA Shuangchen, CHEN Gongda, WEN Jiaqi, MA Lan, JIAO Kunling
    2016, 67(5):  2064-2069.  doi:10.11949/j.issn.0438-1157.20151437
    Abstract ( 79 )   PDF (634KB) ( 165 )  
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    With awareness of environmental protection in recent years, control of greenhouse gas emission has become an important issue. A large port of CO2 come from power plants combustion of fossil fuel, and its capture is necessary for fire-coal power plants. Chemical absorption of CO2 by alkaline absorbent is one of widely use methods. Among the removal technologies of air pollutants by chemical absorbents, ammonia method has many advantages. However, ammonia method has a serious ammonia escape problem, leading to a less favorable selection for the application. The effects of CO2 concentration, ammonia concentration, absorption temperature on ammonia escape were experimentally investigated in the paper. Based on consideration of coordination chemistry principle, some metal ions were selected and studied as additives. The results indicated that addition of Ni2+ showed a good performance for the control of ammonia escape, and it was confirmed by the results obtained by UV-visible spectrophotometer. These results could be valuable for solution of ammonia escape.

    Photocatalytic degradation property of hemicellulose/TiO2 composite gel
    SUN Xiaofeng, LI Chi, XIA Xiuyang, ZHOU Rui, WANG Yaxiong, FENG Yang
    2016, 67(5):  2070-2077.  doi:10.11949/j.issn.0438-1157.20151542
    Abstract ( 116 )   PDF (3958KB) ( 305 )  
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    Hemicellulose/TiO2 composite gel was prepared using hemicellulose and TiO2 nanoparticles. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to study the structure and morphology of the hydrogel. Experimental analysis showed that the hemicellulose was successfully grafted with the polyacrylic acid and a porous hydrogel was observed. The pore size of the hydrogel decreased with the increase of the TiO2 content. In addition, the swelling properties and photocatalytic degradation properties of the hydrogel were also investigated. Experimental results showed that the swelling ratio of the hydrogel increased at first and then decreased with the increase of pH while kept decreasing with the increase of the TiO2 content. The degradation ratio of methylene blue increased at first and then decreased with the increase of the TiO2 content or a rise of pH value of the methylene blue solution, and it also increased with the increase of the initial concentration of methylene blue solution.

    Effect of surfactant-assisted ionic liquid pretreatment on enzymatic hydrolysis of rice straw
    CHANG Ken-Lin, CHEN Ximei, HAN Yeju, WANG Xiaoqin, LI Yunying, WEN Zhang, QIU Xiaosheng
    2016, 67(5):  2078-2083.  doi:10.11949/j.issn.0438-1157.20151450
    Abstract ( 87 )   PDF (992KB) ( 168 )  
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    The enzymatic hydrolysis of lignocellulosic materials is a key stage for fuel ethanol production. Therefore, the pretreatment of lignocellulosic materials (as rice straw) is important to enhance the enzymatic hydrolysis saccharification. In this study, the rice straw was used as raw material and pretreatment by surfactant-assisted ionic liquid. Effects of pretreatment temperature and time, and adding proportion of surfactants on the enzymatic hydrolysis of rice straw were investigated. According to the result, the optimal condition for enzymatic hydrolysis of rice straw was at 110℃ for 60 min with 1% surfactants. To compare with the ionic liquid pretreatment of rice straw, cellulose conversion was increased by 8%—15%. The improvement of enzymatic hydrolysis was confirmed by rice straw composition analysis, FTIR, XRD, SEM of untreated and pretreated rice straw.

    Comparison of different lignin removal processes for corn stover on cellulase adsorption and enzymatic hydrolysis
    TIAN Shunfeng, CHENG Li, GU Zhengbiao, HONG Yan, LI Zhaofeng, LI Caiming
    2016, 67(5):  2084-2092.  doi:10.11949/j.issn.0438-1157.20151570
    Abstract ( 145 )   PDF (667KB) ( 322 )  
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    Experiments were conducted for various pretreated substrates to investigate the impact of lignin content on cellulase adsorption and substrate digestibility. Compared with other treatments, 2% (mass) NaOH pretreated solids with the highest level of lignin removal (85%) exhibited the highest accessibility to cellulase [4.7 mg protein·(g glucan) -1] and enzymatic digestibility (18.9%). The obtained maximum adsorption capacity (Wmax) and equilibrium constant (K) derived from fitting the Langmuir adsorption isotherm for different delignified substrates indicated that the removal of lignin benefited cellulase adsorption. The relationship between cellulase adsorption capacities and enzymatic digestibility for raw and pretreated solids correlated well (R2>0.8), supporting the hypothesis that carbohydrate conversion was primarily dominated by enhancing substrate accessibility owing to lignin removal. Nevertheless, further delignification by NaOH with concentrations of 3% (mass) and 4% (mass) was unfavorable to improving substrate accessibility to cellulase and enhancing carbohydrates conversion to monosaccharide. It appeared that the appropriate delignification to some degree was a significant pretreatment factor to be taken into consideration to achieve more effectively enzymatic digestibility.

    Removal of di-n-butyl phthalate from aqueous solution by MIEX
    WANG Liang, MA Shushuang, ZHAO Bin, LI Junjing, ZHANG Zhaohui, GUO Xingfei, CAO Hongjie
    2016, 67(5):  2093-2100.  doi:10.11949/j.issn.0438-1157.20151319
    Abstract ( 141 )   PDF (622KB) ( 168 )  
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    Di-n-butyl phthalate (DBP) is one of endocrine disrupting chemicals (EDCs), which is commonly found in aquatic environment. In this study, DBP removal by magnetic ion exchange resin (MIEX) was investigated with respect to kinetics, isotherms, charge density analysis, Fourier transform infrared spectroscopy (FT-IR) analysis, X-ray photoelectron spectroscopy (XPS) as well as the effect of accompanying components. The removal of DBP was stable after 20 min, and pseudo-second kinetic model could well depict the removal process. In neutral pH soultion, the maxium uptake capacity of DBP by MIEX was around 0.944 mg·g-1. Since the charge density of DBP was only 2.7×10-3 mmol·mmol-1 at neutral pH, the removal of DBP by MIEX was mainly based on the hydrophobic interaction and hydrogen bonding between MIEX matrix and DBP, instead of ion exchange. High concentrations of accompanying and did not affect the DBP removal. The presence of humic acid (HA) slightly decreased the DBP removal; however, the HA removal by MIEX was not affected at all. As an emerging novel technology for the removal of natural organic matters, MIEX can also remove DBP from aqueous solution. Therefore, it can be applied for drinking water treatment when surface water with complex micropollutants was used as the source.

    Hydrophobic oil filter prepared by dry surface modification of quartz sand
    LIU Guang, WEI Bigui, WU Fuping, CHANG Qing
    2016, 67(5):  2101-2108.  doi:10.11949/j.issn.0438-1157.20151397
    Abstract ( 118 )   PDF (4124KB) ( 300 )  
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    The surface of quartz sand was modified by a dry method using Titanate coupling agent DN101 to improve the hydrophobic property of oil filter. The effects of reaction time, dosage of Titanate coupling agent DN101 and reaction temperature on the performance of the oil filter were studied by single factor experiment. The results show that the quartz sand modified by dry process using DN101 exhibits the best performance when the reaction time is 70 min, DN101 dosage 1.2% and reaction temperature 60℃. Lipophilic-Hydrophilic Ratio (LHR) increases from 1.25 to 11.1, the adsorption capacity has great improvement from 0.17 mg·g-1 to 0.25 mg·g-1 for 15.61 mg·L-1 oily wastewater and the oil removal rate of the modified quartz sand filter improves from 72.6% to 97.8% for 17.3 mg·L-1 oily wastewater. The analysis by SEM, XPS and FTIR shows that the chemical bonding combination of DN101 with the functional groups on quartz sand surface forms a uniform and stable cladding layer on the surface of quartz sand.

    Modeling and experimental verification of air supply system in large power PEMFC
    MA Zhiwen, ZENG Yida, LI Lun
    2016, 67(5):  2109-2116.  doi:10.11949/j.issn.0438-1157.20151377
    Abstract ( 88 )   PDF (2069KB) ( 261 )  
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    Recently, proton exchange membrane fuel cell(PEMFC)as main power source of vehicles is widely concerned. Air compressor is one of important components in a PEMFC system and provides required oxygen and pressure for the cathode in electrochemical reactor of PEMFC. Its working performance has a great influence on the steady and dynamic performance of the fuel cell. Using a 150 kW proton exchange membrane fuel cell system in our laboratory, the working characteristics of its centrifugal air compressor are studied, and an application model for the air supplying system of the fuel cell is established, which involves the centrifugal air compressor. The results of experimental verification indicate that the simulation model can reflect accurately the characteristics of the centrifugal air compressor and the air supplying system. And the model can truly describe the steady control effect of the air system with the centrifugal air compressor in the large power PEMFC as well as the dynamic response of the different control strategies. The model provides theoretical support for the study of the air supply system of high power PEMFC and the corresponding control strategy. The simulation model and experimental results are an important basis and reference for the optimization of the next control strategy.

    Mineral transformation during Zhundong coal combustion by CCSEM
    FAN Bin, YU Dunxi, ZENG Xianpeng, LÜ Weizhi, WU Jianqun, XU Minghou
    2016, 67(5):  2117-2123.  doi:10.11949/j.issn.0438-1157.20151438
    Abstract ( 129 )   PDF (567KB) ( 189 )  
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    The mineralogy of Zhundong coal and its combustion-generated particles were characterized in detail by computer controlled scanning electron microscopy (CCSEM). The experiment was done on a lab-scale drop tube furnace. The results showed that there were calcite, kaolinite, pyrite, pyrrhotite, oxidized pyrrhotite and unclassified minerals in Zhundong coal. The mass fraction of quartz, iron oxide and dolimite increased sharply, while the mass fraction of calcite and unclassified minerals decreased. Also, the behaviors of Na, Fe and Ca as the important elements to the ash deposition, and their particle size distributions were investigated.

    Synthesis and film-forming performance of novel polyurethane aqueous dispersions
    XU Xue, ZHONG Shangfu, ZHU Yan'an, QU Jinqing
    2016, 67(5):  2124-2130.  doi:10.11949/j.issn.0438-1157.20151719
    Abstract ( 155 )   PDF (928KB) ( 259 )  
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    The novel diol chain-extender trimethylol propane monolaurate (TMPLA) was synthesized to prepare novel polyurethane aqueous dispersions (n-PUD),which was used as a coalescent to assist the film forming of high Tg polyacrylate emulsion. Effects of NCO/OH molar ratio, soft/hard segment contents and molar ratio of TMPLA/BDO on assistant-film-forming performance of n-PUD were studied. It was found that the assistant-film-forming ability of PUD was increased with decreasing of NCO/OH molar ratio and hard segment proportions. PUDs modified with TMPLA displayed good assistant-film-forming ability. The optimized conditions to prepare assistant-film-forming n-PUD were as follows: molar ratios of TMPLA/BDO and NCO/OH were 4/2 and 1.3, respectively, mass ratio of soft/hard segment was 55/45, and then the blended latex with m(PUD)/m(PA) 25/75 can form a continuous transparent film at 5℃ without coalescent with a VOC content as low as 30 g·L-1.

    Fabrication and characterization of a novel bismaleimide-benzoxazine resin
    YUAN Wei, SHI Tiejun, XU Guomei, LI Ming, LIU Jianhua
    2016, 67(5):  2131-2137.  doi:10.11949/j.issn.0438-1157.20151496
    Abstract ( 134 )   PDF (1282KB) ( 300 )  
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    A novel bismaleimide-benzoxazine resin(abbreviated as HPM-BOZ)was synthesized by three steps. Firstly, N-p-hydroxylphenylmaleimide(HPM)was prepared from maleic anhydride and p-aminophenol. Secondly, HPM, 4,4-2 amino diphenyl ether (ODA) and paraformaldehyde were used as raw materials to prepare HPM-BOZ with Mannich reaction. Thirdly, a novel bismaleimide-benzoxazine resin was fabricated by a specific curing process. The chemical structure of HPM and HPM-BOZ was characterized by FTIR, 1H NMR and 13C NMR. Section fracture surface of the resin was analyzed by SEM. The curing behavior of HPM-BOZ was characterized by DSC with two peaks at about 235℃ and 266℃ appeared during its curing, respectively. TGA curves demonstrated that HPM-BOZ had excellent thermal stabilities under the condition of nitrogen, which began to decompose at 410℃ with 5% mass loss temperature of 438℃ and obtained 60.2% char yield at 800℃.

    Effects of metallic cation concentration and dispersant on crystal phase of Nd:YAG powders
    JI Xiangbo, JING Wei, ZHU Mingshui
    2016, 67(5):  2138-2143.  doi:10.11949/j.issn.0438-1157.20151835
    Abstract ( 58 )   PDF (3594KB) ( 408 )  
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    The effects of metallic cation concentration and dispersant on the crystal phase of Nd:YAG powders were studied. The powders were prepared by co-precipitation with ammonium hydration carbonate as precipitator. The crystal phase of Y2O3, YAM was observed at 0.16 mol·L-1 and 0.32 mol·L-1 of the metallic cation concentration. The solution with pH 8.0 and 0.08 mol·L-1 metallic cation concentration was suitable for the preparation of the Nd:YAG nanopowders. A small amount of sulfate ions dispersant influenced the dispersion and the phase transformation of the precursor during the calcining process. Nd:YAG transparent ceramic with high in-line transmittance was obtained by sintering the green body prepared by co-precipitation powder. 1.6 W laser output at 1064 nm was obtained with a 6 W pump power.

    Numerical simulation of morphology and kinetics of polyethylene in shear flow
    RUAN Chunlei, LIU Chuntai
    2016, 67(5):  2144-2151.  doi:10.11949/j.issn.0438-1157.20151472
    Abstract ( 78 )   PDF (893KB) ( 151 )  
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    The mathematical model of morphology evolution of spherulites and shish-kebabs in the shear flow is deduced based on the Eder model. The model considers that the nucleation and growth of spherulites are determined by the static temperature, while the nucleation and growth of shish-kebabs are determined by the flow, which is depended on the first normal stress difference of the system and the shear rate respectively. In order to calculate the nucleation density of the shish-kebabs, the two-phase suspension model of Zheng is introduced. The model treats the stress as the combination of the amorphous phase and semi-crystalline phase. The amorphous phase is described by FENE-P model while the semi-crystalline phase is depicted by a rigid dumbbell model. Based on the mathematical model, the Monte Carlo method and the finite difference method are constructed, respectively. The former is to capture the crystal growth while the latter is to calculate the equation of the system. By using these methods, the 2D crystallization in the shear flow is simulated. The evolution of spherulites and shish-kebabs is given. Also, the effects of shear time and shear rate on the nucleation density of shish-kebabs, crystallization rate, the viscosity of the fluid and the system stress are discussed. Numerical results show that the Monte Carlo method is valid which not only captures the morphology evolution of crystals successfully, but also predicts the crystallization rate well. In addition, the increase of the shear time or the shear rate will increase the nucleation density of shish-kebabs and the crystallization rate.

    Preparation and property of waterborne polyurethane-based ITO etching ink
    HUANG Jiajian, ZHONG Yingli, ZHOU Chuang, ZHOU Jian, YANG Zhuohong, YUAN Teng
    2016, 67(5):  2152-2160.  doi:10.11949/j.issn.0438-1157.20151638
    Abstract ( 106 )   PDF (6648KB) ( 319 )  
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    Waterborne polyurethane (WUP) is prepared by using polyethylene glycol (PEG) and isophorone diisocyanate (IPDI) as the raw materials, 2,2-bis (hydroxymethyl) propionic acid (DMPA) as the hydrophilic chain extender agent, 1,2-propylene glycol (PDO) as the chain extender, HEA as end-capping reagent and triethylamine (TEA) as the neutralizer. The resin properties are characterized by thermal gravimetric analysis instrument and particle size analyzer. The results show that when the mass fraction of DMPA is 3%—6%, the PU resin has low molecular weight, good water solubility, good heat resistance and suitable particle size. In the preparation of water-based ITO etching ink, PU is the connection material, phosphoric acid or the compound of phosphoric acid and sulfuric acid is the etching agent, kaolin is the filler, defoamer and leveling agent are the additives. The properties of the ink are characterized. The results show that the best ink formula is that the mass fraction of etching agent is 25%—30%, the mass fraction of connection material is 30%—45%, the mass fraction of filler is 30%—45% and the mass fraction of additives is 1%. The best etching process is that the etching temperature of ITO film is 120℃, the etching time is 20 min and the ink-cleaning time is 50 s, while the etching temperature of ITO glass is 150℃, the etching time is 20 min and the ink-cleaning time is 50 s. The particle size distribution of the ink is 10—50 μm, the dehydration rate of the ink is just 1.12%—3.68% after 3 h, and the viscosity and pH of the ink are almost stable after 60 d. The etching ability of the ink does not reduce with increasing time, and the lines' image resolution of screen printing is significantly better than the commercially available water-based ink.

    Direct electrochemistry of immobilized glucose oxidase on amorphous mesoporous zirconium phosphate
    YU Zhihui, HUANG Pengfei, WANG Xiayan
    2016, 67(5):  2161-2168.  doi:10.11949/j.issn.0438-1157.20151475
    Abstract ( 92 )   PDF (1993KB) ( 241 )  
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    Glucose oxidase (GOD)/zirconium phosphate(ZrP)/glassy carbon(GC) electrode was prepared by adsorbing GOD on the amorphous mesoporous zirconium phosphate. The electrocatalytic properties of GOD/ZrP/GC electrode were characterized by cyclic voltammetric method at the medium of phosphate buffer (0.1 mol·L-1). The results showed that there were quicker electron transfer rate and larger surface coverage when GOD was supported on zirconium phosphate. At the same time, the electrochemical device with this electrode showed faster current response and higher sensitivity in detection of glucose, indicating that zirconium phosphate could be more suitable support for immobilization of GOD and achieve better performance of direct electrochemistry.

    Synthesis, physical-mechanical properties and fire behaviors of polyurethane foam with reactive flame retardant and expandable graphite
    YANG Rong, QIAO Hong, HU Wentian, XU Liang, SONG Yan, LI Jinchun
    2016, 67(5):  2169-2175.  doi:10.11949/j.issn.0438-1157.20151564
    Abstract ( 89 )   PDF (1495KB) ( 196 )  
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    Flame retardant polyurethane foams have been synthesized by using a new reactive flame retardant hexakis (4-diethyl phosphate hydroxymethyl phenoxy) cyclotriphosphazene (HPHPCP) and expandable graphite (EG). The effects of flame retardants on physical-mechanical properties, thermal stability and fire performances were investigated. In particular, the fire behaviour of the foams was studied by the oxygen index and UL-94 burning test. The results showed that the density of flame retardant foams increased with flame retardant compound. The compressive strength increased first and then declined with the decrease content of HPHPCP. However, an increase in the content of expandable graphite caused a worsening of insulating properties of PUF. The presence of HPHPCP mixture with EG brought an overall improvement in the thermal stability and fire behavior. The initial decomposition temperature (T10%), maximum decomposition temperature (Tmax) and char residues at 700℃ increased with increasing content of EG in mixture flame retardant. Moreover, the oxygen index (OI) increased in a linear way and all flame retardant PUFs can pass UL-94 HF-1 and V-0 rating.

    Detonation flame propagation and quenching characteristics in crimped-ribbon flame arrester
    SUN Shaochen, BI Mingshu, LIU Gang, DENG Jinjun
    2016, 67(5):  2176-2184.  doi:10.11949/j.issn.0438-1157.20151383
    Abstract ( 120 )   PDF (644KB) ( 262 )  
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    A self-designed explosion suppression experimental system including sensor detection system, gas mixing equipment, data acquisition device and electric spark ignition device was set up to investigate various fuel/air premix detonation flame propagation and quenching by crimped-ribbon flame arresters in horizontal pipe that closed at both ends. Detonation experiment showed that when the concentration of flammable gas was close to the stoichiometric ratio, (4.2% propane, 6.6% ethylene and 28.5% hydrogen, percentage by volume), the evolution process from ignition to flame quenching was very short. It could be divided into four stages: slow rise, quick rise, accelerate rise and pressure fluctuation. The peak detonation pressure for propane-air and ethylene-air was higher in D 80 mm flame arrester than other diameters. When pipe diameter increased to 400 mm, the detonation pressure was decreased gradually, especially for ethylene-air the pressure was only about 3 MPa. However, the peak detonation pressure of hydrogen-air was gradually increased with the increase of the pipe diameter. The result on detonation velocity indicated that its value for the premixed gas of propane-air was quite close to ethylene-air, even a little higher. However, the value of hydrogen-air premixed gas was relatively high. With the increase of the pipe diameter, the detonation velocity tended to be more stable due to the wall heat loss, the resistance factors and some other reasons. At the same time, it might be expected that the detonation safety flame velocity would be proportional to element thickness base on the classic theory of the heat transfer. Then, by using the experimental data, the detonation safety flame velocity calculation method was derived, which would provide more accurate reference for design and selection of crimped-ribbon flame arrester.