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Table of Content
05 November 2011, Volume 62 Issue 11
    综述与专论
    Fabrication techniques and stack assembling methods for micro tubular solid oxide fuel cells
    MENG Xiuxia, YANG Naitao, YIN Yimei, TAN Xiaoyao, MA Zifeng
    2011, 62(11):  2977-2986. 
    Abstract ( 1989 )   PDF (1440KB) ( 1422 )  
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    Micro tubular solid oxide fuel cells (MT-SOFCs)have not only the inherent benefits of SOFCs, but exhibit new advantages over conventional SOFCs, such as higher mass transfer/heat transfer, higher reaction efficiency, rapid start-up/shut-down and significantly reduced volume. Therefore, MT-SOFCs show potential applications in portable and mobile power sources. This paper reviews the progress of MT-SOFC studies, focusing on the properties, structures, and fabrications of the cells. The structures and performances of MT-SOFCs supported with electrolyte, anode and cathode respectively are compared and analyzed. The key step for fabrication of MT-SOFCs is the preparation of micro tubes using methods such as isostatic pressing, plastic extrusion and phase inversion spinning methods for hollow fiber ceramics.  Preparation of dense electrolyte membrane and assembling of cell stacks are discussed. The challenges and potential applications of MT-SOFCs in portable power sources, electric vehicles and micro reactors are also highlighted.

    热力学
    Thermodynamics of nanofluid boiling nucleation
    LI QimingWANG BuxuanDUAN Yuanyuan
    2011, 62(11):  2987-2992. 
    Abstract ( 1512 )   PDF (469KB) ( 985 )  
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    Based on the classical nucleation theory, nanofluid is considered to be a nanoparticle-uniform-distribution system. Clustering and deposition of particles are ignored. A nanoparticle is analogous to a molecule, base fluid is analogous to solvent, and nanofluid is analogous to a dilute solution. Nanoparticles absorbed at the vapor-liquid interface were assumed to be embedded at the interface, partially in the vapor and partially in the liquid. The distribution of nanoparticles at the interface was assumed to be uniform. Using the thermodynamic theory of solution, homogeneous and heterogeneous nucleation models of nanofluids were then developed to discuss nanoparticles effect on nucleation. The results showed that nanoparticles accumulation at the vapor-liquid interface decreased embryo bubble radius and the potential barrier of nucleation, facilitating liquid nucleation.

    流体力学与传递现象
    Rayleigh convection and its effect on interfacial mass transfer by lattice Boltzmann simulation
    FU Bo, YUAN Xigang, CHEN Shuyong, LIU Botan, YU Kuotsung
    2011, 62(11):  2993-3000. 
    Abstract ( 1360 )   PDF (1967KB) ( 1008 )  
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    In an interfacial mass transfer process, the concentration gradient of the transferred component builds up in the vicinity of the interface. The concentration gradient may generate density difference near the interface. If the density gradient directs opposite to the gravity, the interface is known as in Rayleigh instability and Rayleigh convection may occur in case of perturbation. Rayleigh convection is an interfacial phenomenon usually observed in mass transfer processes and in material processing industries. In this study, a two-dimensional lattice Boltzmann method (LBM)is implemented for simulating Rayleigh convection, which is induced by interfacial mass transfer in the CO2 absorption into liquid ethanol. The computations of concentration and velocity fields are based on a two-distribution model, which consists of the concentration and the density distribution functions of fluid particles in the lattice Boltzmann method. And the gravity difference due to the concentration difference is introduced into the model as external force. The established method is used for the simulation of two-dimensional liquid-phase Rayleigh convection induced by multiple discrete diffusion sources of CO2 on the gas-liquid interface. The simulation results show that the concentration contours are consistent with the experimental results in literature. The effects of Rayleigh convection on the transport mechanisms are investigated by analyzing the Rayleigh convection and concentration contour patterns. By simulating the concentration field with the LBM, the instantaneous interfacial mass transfer flux of CO2 can be obtained. It is demonstrated that when the Rayleigh convection occurs, the instantaneous interfacial mass transfer flux increases in the beginning and then decreases with time. Such behavior may be affected by the Rayleigh convection patterns and their evolutions.
    An analysis for heat and moisture transfer effect in air-water or -hydroscopic solution ()Reachable handling region
    ZHANG TaoLIU XiaohuaJIANG Yi
    2011, 62(11):  3001-3008. 
    Abstract ( 1131 )   PDF (1520KB) ( 260 )  
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    A model is established to analyze the heat and moisture transfer process in air-water or - hydroscopic solution system, two independent driving forces each other: enthalpy difference and relative humidity difference can be obtained. A triangle region, consisting of iso-enthalpy line from air inlet, saturation line of moisture air(iso-concentration line of solution)and connecting line of air and water or solution at inlet status, is determined in enthalpy-psychrometric chart based on relationship between the two driving forces. The region is a reachable handling region for heat and moisture transfer process in air-water or-hydroscopic solution system, because the variation of air outlet status is limited in the region whatever change of mass and heat transfer coefficients or flow pattern and rate. Experimental results of dehumidification and regeneration in literatures are analyzed with the help of reachable handling region.

    An analysis for heat and moisture transfer effect in air-water or -hydroscopic solution ()Characteristic zones of mass transfer
    ZHANG TaoLIU XiaohuaJIANG Yi
    2011, 62(11):  3009-3016. 
    Abstract ( 989 )   PDF (1819KB) ( 571 )  
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    The effects of heat and moisture transfer process are calculated on some typical points having different positions from the inlet in air-water or -hydroscopic solution system. Based on the effects and the direction of mass and total heat transfer as well as the correlations between them, the mass and total heat transfer process can be divided into four zones for air-hydroscopic solution(zone A—zone D), and three zones for air-water(zone A—zone C) for air-water. The transfer characteristics for heat and moisture in different zones are analyzed, the flow pattern of better effect of mass transfer is obtained and the boundary lines between the zones are determined. The process for air humidification and solution regeneration are optimized with the help of reachable handling region as well as the results of heat and moisture transfer, indicating that heat should be put into water or solution rather than air to get better air humidification and regeneration.

    Work recovery efficiency of work exchange in chemical process
    DENG Jianqiang, MA Li, FENG Xiao
    2011, 62(11):  3017-3023. 
    Abstract ( 1385 )   PDF (409KB) ( 548 )  
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    Whenever a high-pressure fluid stream, or simply stream HP, is depressurized, a potential for mechanical energy recovery exists. On the other hand, pressurizing a low-pressure fluid stream, or simply stream LP, always requires mechanical energy. In principle, a work exchanger (WE)may be applied to any high-pressure processing systems where it is also desirable to recover mechanical energy to offset the energy requirement for pressurization of low pressure streams. Because the gas streams in the chemical process often appear with big flux and high pressure, there are great potential to recover work in the process industry. But, it is difficult to forecast and appraise the work recovery result between two gas streams because gas is compressible. For the two kinds of structure of gas-gas WE, the reciprocating machine and the centrifugal machine, their thermodynamic processes were analyzed and the equations of work recovery efficiencies were proposed. The in-depth simplified work recovery efficiency equations of the work transfer process in two WE structures were presented through reasonable assumption and were compared finally. The work recovery efficiency equation of centrifugal machine was also extra influenced by initial volume flow ratio than the reciprocating machine. In order to see what pure influence of the stream phase state on the work recovery efficiency, the influence of initial volume flow ratio was expected to be neglected. So the reciprocating machine was chosen to take as example and its performance of work exchange between two streams with different phase states were compared. Two WE structures corresponded to different work recovery efficiency equations. The simplified work recovery efficiency equation of reciprocating machine followed a power function of compression ratio. Its work recovery efficiency decreased with increasing compression ratio, while for centrifugal structure, the work recovery efficiency was relevant to not only pressure ratio but also initial volume flow ratio. Furthermore, because the centrifugal structure did not involve minimal pressure differential, a centrifugal machine could achieve higher LP compression than a reciprocating machine. The present work compared the work recovery efficiency between the streams with different phase states. The result showed that with the same compression ratio and initial volume flow ratio, liquid-liquid reciprocating work exchanger had the highest work recovery efficiency value. Its ideal value was 100%. The work recovery efficiency values of gas-liquid WE and liquid-gas WE decreased successively, while the value of gas-gas WE was the lowest. The work recovery efficiency equation of centrifugal machine had also extra influence by initial volume flow ratio than the reciprocating machine.

    Effects of pore characteristics of fractal porous media on gas diffusion
    CHEN YongliCAO LiyongHE WeiHE Rong
    2011, 62(11):  3024-3029. 
    Abstract ( 1278 )   PDF (711KB) ( 640 )  
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    Porous particles used in combustion or catalysis were made by random walk method. The fractal characteristics of the porous particles are close to that of real ones. Based on the particle model, gas diffusion was investigated in the porous particles. Diffusion control equations were established according to the kinetic theory of gases and statistical thermodynamics. The effect of pore characteristics on gas diffusion was analyzed. The relationships between the specific area, average pore diameter and porosity with the diffusion coefficient were obtained. The results indicate that the gas diffusion coefficient decreases with the increase of specific area of pores. Gas diffusion coefficient increases as a power function of average pore diameter, and the exponent that represents the sensibility decreases linearly with the increase of porosity.

    Surface temperature distribution of droplet heated by local microheater
    HU DinghuaWU HuiyingWU Xinyu
    2011, 62(11):  3039-3045. 
    Abstract ( 1061 )   PDF (2328KB) ( 600 )  
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    The temperature distribution of droplet surface directly influences the microflow inside the droplet, but most of the papers about droplet surface temperature are based on substrate heating mode. In this study, with the aid of the infrared thermograph and MEMS technology, both the surface temperature and the temperature gradient of the droplet were investigated based on local heating mode. It was found that different from the concave distribution of surface temperature in the substrate heating mode, the surface temperature of the droplet in the local heating mode showed a convex distribution with a higher temperature at the apex but a lower temperature at the edge. With the increase of heating power, both the surface temperature and the temperature gradient were increased. However, as the heating power reached a certain value, the surface temperature gradient increased less and finally tended to a uniform distribution.  The surface temperature of the droplet before and after the bubble burst under local boiling was also investigated. The results presented in this paper help to understand the internal microflow of droplets in the local heating mode and manipulate the microflow inside droplets.

    Thermal performance of micro pulsating heat pipe
    QU Jian, WU Huiying
    2011, 62(11):  3046-3052. 
    Abstract ( 1260 )   PDF (1310KB) ( 547 )  
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    This paper presents an experimental investigation on the thermal performance of a micro pulsating heat pipe (MPHP)embedded on a silicon wafer with the trapezoidal cross section having a hydraulic diameter of 352 μm. With FC-72 and R113 as working fluids, the effects of gravity, filling ratio, and working fluid on the thermal performance of MPHP are discussed. Experimental results show that the MPHP functions well at its hydraulic diameter or a Bond number about 0.45. Gravitational effect on the thermal performance cannot be ignored although it is small in comparison with the surface tension effect. At an inclination angle larger than 10°, the MPHP works as a true pulsating device when the filling ratio varies from 30% to 65%, enhancing the heat transfer capacity effectively. For FC-72 and R113, the optimal filling ratio is 55% and 41%, respectively, for the best thermal performance of the MPHP. The heat transfer capability of the MPHP is significantly enhanced and the thermal resistances is reduced up to about 56. 5% (FC-72)and 59. 7% (R113)at a power input of 8.5 W with the corresponding optimal filling ratios when compared to the unfilled MPHP(0 filling ratio).It is also found that R113 is fit for the MPHP at lower heat loads, while FC-72 is favorable at relatively higher heat loads.

    Affecting factors of Marangoni condensation mode
    HU ShenhuaYAN JunjieWANG Jinshi
    2011, 62(11):  3053-3059. 
    Abstract ( 1274 )   PDF (2558KB) ( 619 )  
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    The effect of macroscopic temperature gradient on Marangoni condensation of ethanol-water vapor mixture was investigated experimentally in a wide range of concentration(0—50%)at different velocities (2, 4, and 6 m·s-1)and pressures (31.2, 47.4, and 84.5 kPa)with shot condensation modes. An oblique copper block was employed to create surface temperature gradient. Six condensation modes were observed in the experiments, which are smooth film, bulk-drop, drop-streak, drop, wavy-drop and streak. Not every condensation mode appeared in each process and some condensation behavior was not distinct. For low condensation (0.5% and 1%)and high condensation (50%)smooth film was observed under the condition of large vapor-to-surface temperature difference. Drop mode occurred easily at high concentration ( >20% )while bulk-drop was a regular condensation mode at the concentration of 0.5%, 1% and 2%. Drop-streak and streak could occur almost at all concentrations with low vapor-to-surface temperature difference ( <3 K).In the wide range of vapor-to-surface temperature difference, bulk-drop was a principal condensation mode. Condensation modes could vary with some factors, such as vapor-to-surface temperature difference, ethanol mass fraction, vapor velocity, and vapor pressure, especially the former two. The heat transfer coefficients depended on the condensation behavior. In general, for low ethanol concentration (0.5% and 1%), the heat transfer coefficients could keep a large value over a relative wide range of vapor-to-surface temperature difference. The maximal heat transfer coefficients corresponded to the dropwise condensation mode and small heat transfer coefficients to the filmwise or rivulet modes. In addition, the condensate drops became smaller and denser with the increase of vapor pressure or velocity. The effect of vapor pressure on condensation behavior was less than that of vapor velocity. Meanwhile, the movement of drop or streak biasing from left to right could be observed in the experiments. For the condensation modes on flat plate and oblique block, it was found that the condensation modes on oblique block was more irregular, and condensation behavior could not be simply classified into certain mode, such as drop, streak, ring like, filmwise and film with fluctuate, since each mode may play a part in the condensation or condensation behavior is an intermediate transition state in various condensation modes.

    Thin-film thermocouples for rapid measurement of transient surface temperature in cryogen spray cooling
    ZHOU Zhifu, WU Weitao, WANG Guoxiang, CHEN Bin, WANG Yueshe, GONG Zheng
    2011, 62(11):  3060-3065. 
    Abstract ( 1305 )   PDF (1591KB) ( 814 )  
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    Pulsed cryogen spray cooling (CSC) has become an effective method to protect the epidermis from non-specific thermal injuries in laser treatments of vascular malformation such as port wine stains. Cooling experiments with a skin phantom are usually conducted to quantify the heat transfer of CSC from a skin surface. Due to the high cooling ability of CSC and poor thermal conductivity of the skin phantom, the skin surface usually experiences a fast variation of the surface temperatures during CSC. It is therefore desirable to have a fast response surface thermal sensor to measure such temperature change. In traditional methods, commercial thermocouples of round or plate-shaped joints are buried on the surface or within the skin phantom in the experiments and usually give a poor response of the surface temperature. In this study, a fast response, thin film thermocouple (TFTC) of type T on a skin phantom made of epoxy or plastic glass is developed. The thin film thermocouple is manufactured by the Magnetron Spurting technique with a precise control of the compositions of Cu and Ni as well as the film thickness from 0.5 to 2 microns. A 0.05 micron thick of SiO2 protection layer is deposited on the TFTC as protection. Careful calibrations of TFTCs indicate that the thermoelectric property of the TFTCs agrees well with that of standard T-type thermocouples. The time constant of the TFTCs is about 1. 2 ms, determined by pulsed laser heating experiments. Due to its small thermal capacity,the TFTC is sensitive to environmental fluctuations and the original temperature data show large noises. A low pass Butterworth (BW) filter is then introduced in the data acquisition system to remove such noises. Effect of the cut-off frequency and sample rate on the filtered temperature data has also been investigated and optimal cut-off frequencies and sample rates are recommended. A typical result for the temperature variation of the epoxy phantom surface during CSC is presented to illustrate the effectiveness of our TFTCs.

    Composition shift analysis of zeotropic mixed refrigerant in refrigeration cycle
    XU Xiongwen, LIU Jinping, CAO Le, QIN Yan, QIU Guoxiong, DENG Xue
    2011, 62(11):  3066-3072. 
    Abstract ( 2005 )   PDF (427KB) ( 570 )  
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    Zeotropic mixed refrigerant is widely used in Joule-Thomson refrigeration cycles, and refrigerator performance is greatly affected by the composition shift of mixed refrigerant. Based on conservation equations,a mathematical model of mixed-refrigerant composition shift in gas-liquid two-phase flow is proposed in this paper. The deduction result shows that different velocity of gas and liquid in the two-phase flow is the necessary condition of local composition shift. Then, the composition shift principle is obtained, and with the composition of circulated refrigerant, local refrigerant composition is calculated and verified by a mixed-refrigerant shift experiment in the evaporator of Joule-Thomson refrigerator. The results show that in gas-liquid two-phase flow, if the jth refrigerant component fraction sharing in gas is greater than that in liquid, the local concentration will be less than the circulated concentration, vice versa. Therefore,the local concentration of low boiling point component is less than circulated concentration in Joule-Thomson refrigeration cycle, while that of high boiling point component is greater than the circulated one. Further analysis shows that circulated concentration of low boiling point component is greater than charged fraction, while that of high boiling point component is less than the charged fraction. Thus,in order to achieve the predetermined mixed-refrigerant composition, more high boiling point component needs to be injected into the system.

    Partial spectrum k-distribution model for radiative property of flue gas with soot and flyash from oxygen-enriched combustion
    LI Haoyu, YAN Weiping
    2011, 62(11):  3073-3080. 
    Abstract ( 1805 )   PDF (590KB) ( 503 )  
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    A new partial spectrum k -distribution model is developed for oxy-fired boilers, characterized by larger pressure path-lengths and possibly different ratios of water vapor and carbon dioxide compared to air-fired boilers. In this model spectral regions with similar background properties are grouped into M partial spectrum distributions, in which the k distribution absorption coefficients of mixture are produced from multiplication approach. The absorption coefficients of gas are assembled from a narrow-band k -distribution database, but the scattering and absorption coefficients and phase function of particle are predicted by Mie theory. The radiation source and wall flux between two cold black parallel plates and for one signal spectral path and a two-dimensional rectangular system are calculated to verify the present model by combination of the present model and the discrete ordinate method in the furnace of flue gas with soot, flyash, high concentration of water vapor and carbon dioxide gas under oxygen-enriched coal combustion mode. The results from the present mode are more reasonably consistent with those by the line-by-line method. Moreover, the accuracy of the present model is higher and the computation time is reasonable compared with full-spectrum correlated- k distribution and wide band correlated- k model. It seems that this new partial spectrum k -distribution model is suitable for oxygen-enriched flue gas with flyash.

    Optimization and simulation of sinter cooling process
    ZHANG Xiaohui, ZHANG Jiayuan, DAI Chuande, XIE Dongjiang
    2011, 62(11):  3081-3087. 
    Abstract ( 1492 )   PDF (726KB) ( 782 )  
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    Through studying a 360 m2 sinter cooler in an iron and steel company, a mathematical model for heat transfer in sinter cooling process is established. This model is based on the porous medium model, in which the momentum equation is corrected by Ergun equation and the energy equation is corrected by the two energy equations for local non-equilibrium thermodynamics. This model is solved with the user defined functions (UDF)and the user defined scalars (UDS)in the platform of computational fluid dynamics software, Fluent6.3. The sinter size, inlet velocity, material height, porosity and inlet temperature are the main parameters affecting the waste heat recovery efficiency. The five parameters are simulated and their optimal combination is determined by orthogonal experimental method for improving the waste heat utilization, which are as follows: sinter size 0.025 m, inlet velocity 7.65 m·s-1, material height 1.8 m, porosity 0.45, and inlet temperature 414 K. This model is verified reliable by comparison with the test data. The method can be used for design of sinter coolers.

    Optimization and field synergy analysis for inner flow field of curved tube based on entransy extreme principle
    CHEN Hongyu TIAN Maocheng LENG Xueli ZHANG Guanmin QIU Yan
    2011, 62(11):  3088-3092. 
    Abstract ( 1498 )   PDF (3840KB) ( 875 )  
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    Entransy dissipation extreme principle is used to simulate the optimized laminar flow field in a curved tube numerically. Adjusted N-S equations with additional force are derived. The additional forces derived from the entransy dissipation extreme principle does not exist in real world and can be only used in calculations. When the governing equations change, different numerical result with same boundary conditions will be obtained, which is defined as the optimized flow field. The ordinary laminar flow fields in the same curved tube with the same boundary conditions are also calculated. The comparison between the ordinary flow field and the optimized one is made and the difference between the two flow fields is analyzed based on the field synergy principle. The result indicates that the additional force changes the flow pattern in the inner curved tube from ordinary laminar flow to symmetrical intense helical flow. The heat transfer performance evaluation criterion(PEC)value is more than 1.7 while the temperature gradient field becomes more uniform, and the cosine of field synergy angles around the boundary layer is increased, improving the surface heat transfer coefficient greatly. The optimized flow field improves the field synergy characteristics and enhances the heat transfer and can be utilized in development of heat transfer enhancement and energy saving techniques.

    Unsteady flow characteristics in low-specific-speed centrifugal pump with complex impeller
    CUI Baoling, XU Wenjing, ZHU Zuchao, LIN Huichao
    2011, 62(11):  3093-3100. 
    Abstract ( 1470 )   PDF (3182KB) ( 1844 )  
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    To investigate the unsteady flow characteristics caused by interaction between the impeller and volute in the low-specific-speed centrifugal pump, the unsteady flow field of a centrifugal pump with four-long and eight-short blades was simulated based on sliding mesh and RNG k-ε turbulence model. The simulation results of velocity and static pressure show highly asymmetric in space as well as highly unsteady in time. The velocities on sections and of volute have the same trend, and the circumferential velocity decreases along the radial direction of volute. The change of radial velocity magnitude on section is less than that on section because section is away from the tongue and is less influenced. The flow near the volute is the most complex and the radial negative velocity appears on section . The rotor-stator coupling is the main reason for pressure fluctuation, whose frequency is dominated by impeller rotating frequency, and the dominant frequency is blade passing frequency. The amplitude of fluctuation pressure along the volute fluctuates from section to section , and its average value declines gradually until section reaches a minimumvalue. Compared with the steady calculation, the effective head calculated by unsteady calculation is closer to experimental value at design point, indicating that the unsteady calculations can predict the pump head accurately.

    Lattice-Boltzmann simulation for bubble pulsatile flow in capillary tube
    MA Qiang, ZHANG Ying, ZENG JianbangHAN Jingxiao, JIA Guorui
    2011, 62(11):  3101-3108. 
    Abstract ( 1344 )   PDF (1612KB) ( 840 )  
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    Based on the theory of pseudo-potential, an isothermal lattice-Boltzmann model for multiphase pulsatile flow in capillary tube was established. By selecting the appropriate dimensionless parameters, the simulation unit was loaded into an actual unit. Simulation results obtained by this model, such as surface tension of static drop, shape of rising bubble in large space and narrow space, were compared with theory and other scholars research results, and the reliability of this model was verified. Bubbly flow driven by the sinusoidal pressure wave in capillary tube was simulated. The relationship between pressure wave amplitude and periodic variation of liquid phase Re number and bubble displacement was investigated. Shape changes of vapor-liquid interface in the periodic pulsatile process was obtained. The oscillation of Re number near the boundary area was observed when the direction of liquid velocity on the boundary was changed.  The reason for this phenomenon was discussed in this paper. The effect of gravity on the pulsatile process was analyzed. Simulation results validated the empirical law that the flow pattern in the capillary tube was affected by gravity if Bond number (ratio of buoyancy force to surface tension force) Bo >2. The movement and interface form of a single liquid slug was alsoinvestigated by using numerical simulation. The research result agreed with experimental results from literatures. These simulation results provided the basis for the research of pulsatile heat pipe with capillary tube as its main component.

    Influences of air pipe parameters on thermal working conditions in carbon rotary kilns
    CHEN Wenzhong, WANG Chunhua, LIU Baoyu, JIA Fengrui, TIAN Yuanhang
    2011, 62(11):  3109-3114. 
    Abstract ( 1228 )   PDF (1449KB) ( 669 )  
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    Taking a 2.3 m×55 m carbon rotary kiln for example, numerical simulations were conducted on gas and solid spaces of the kiln by using Fluent and Matlab softwares. Through changing air pipe length and air flow of secondary and tertiary air, temperature field distributions and gas concentration distributions were obtained under different conditions. The results indicated that air pipe length had insignificant influence on kiln temperature, so air could be supplied without pipe in practical engineering to resolve the burning out of air pipe. When the length of air pipe equaled a specific value, kiln temperature was up to a higher temperature. At the same time, the concentration of the remaining combustible gas was lower under that condition. As the secondary and tertiary air flowed to the kiln outlet, the remaining combustible gas was higher at the kiln inlet, but the temperature of the calcining zone was higher, and the length of the calcining zone was longer.  Conversely, the remaining combustible gas was lower at the kiln inlet, the temperature of the calcining zone was lower, and the length of the calcining zone was shorter as the secondary and tertiary air flowed to the kiln inlet.

    Helical vortices in circular pipe with twisted tape
    LIU WenLUO ZhengyuanBAI Bofeng
    2011, 62(11):  3115-3122. 
    Abstract ( 1239 )   PDF (3793KB) ( 1567 )  
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    Short twisted tape as a modified twisted tape can reduce pressure drop significantly,however, the secondary flow characteristics are unclear. To explore the features of flow induced by short twisted tape in a circular pipe, water in turbulent flow and gas-liquid two-phase flow for the short twisted tape in a pipe was numerically simulated with Fluent software. The effects of helical vortices on the flow and the effects of Reynolds number on helical vortices were investigated by RSM turbulence model and Euler multiphase model. The results showed that the secondary structure induced by the short twisted tape was two central symmetric helical vortices. Helical vortices affected significantly the main flow field. Helical vortices increased the tangential velocity near the pipe wall, while decreased the tangential velocity near the pipe center. Axial velocities near the pipe center and the wall were low, and two high axial velocity areas appeared away from the twisted tape. Reynolds number affected helical vortices, and the pitch of helical vortices decreased with increasing Reynolds number. In the gas-liquid two-phase flow, helical vortices remarkably affected liquid distribution, including droplets and liquid film in full pipe region, and liquid volume fraction was high in the helical vortices region while low far away from the helical vortices. The effects of helical vortices on gas-liquid two-phase flow were different from single phase flow. The axial velocity profile tended towards the parabolic shape of laminar flow, and gas axial velocity significantly increased compared to the smooth pipe. Liquid distribution was not located near helical vortices center.

    Numerical simulation of solid dissolution process considering unsteady natural convection
    HU Chengyao, HUANG Pei
    2011, 62(11):  3123-3129. 
    Abstract ( 1183 )   PDF (2300KB) ( 603 )  
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    To reveal the flow structure, mass transfer and solid surface morphology in the solid dissolution process by considering unsteady natural convection, a two-dimensional mathematical model of solid-liquid dissolution process was established based on theories of dissolution kinetics and mass transfer. The finite element software COMSOL was used to investigate the effect of Rayleigh number on the flow, mass transfer and solid surface morphology. The results showed that the method might well capture the interface motion and position caused by dissolution, and obtain the propagations of flow structure and mass transfer. At a low Rayleigh number(104), viscose force is generally more dominant than buoyancy force and diffusion is the principal mode of mass transfer whereas at a higher Rayleigh number, convection is the dominant mass transfer mechanism. As a result, natural convection significantly enhanced mass transfer, and led to nonlinear dissolution. The solid surface morphology depended not only on Rayleigh number but also time.

    催化、动力学与反应器
    Indirect thermal coupling between methane combustion and dodecane dehydrogenation reactions
    LU ZexiangJI Shengfu, LIU HuiLI Chengyue
    2011, 62(11):  3130-3135. 
    Abstract ( 1241 )   PDF (765KB) ( 458 )  
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    Metallic monolith catalysts, Pd-Zr/SBA-15/Al2O3/FeCrAl and Pt-Sn-Li/Al2O3/FeCrAl, for the exothermic catalytic combustion of methane and the endothermic dehydrogenation of dodecane were placed respectively into the inner tube and annular space of a tubular jacket reactor that could be heated by an external electric furnace. Their thermal coupling was tested. The experimental results showed that the oven temperature was slightly lower than that of the metallic monolith catalyst beds, indicating that the heat required for dodecane dehydrogenation reaction came indeed from that released by methane combustion, at least mostly, and thus demonstrating indirect thermal coupling between the two reactions taking place on the metallic monolith catalysts. Under the reaction conditions of pressure 0.1 MPa, oven temperature 743.15 K, GHSV 7.5 ml·m-2·h-1(3.5% CH4/air feed), C12H26 LHSV 0.315 ml·m-2·h-1, and molar ratio of hydrogen to alkane 4, methane was converted at 100%, C12H26 conversion was 6.3%, and C12H24 selectivity was 71.5%.

    Biosynthesis of glycyrrhetic acid 3-O-mono-β-D-glucuronide by whole cell in ionic liquid/water biphasic system
    CHEN Jinyan, ZOU Shuping, HE Dongmei, YANG Xiaogang, LI Chun
    2011, 62(11):  3136-3142. 
    Abstract ( 2073 )   PDF (996KB) ( 105 )  
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    Glycyrrhizin (GL), the biologically active compounds of liquorice, can be hydrolysed to glycyrrhetic acid 3-O-mono-β-D-glucuronide (GAMG)by whole cells containing β-D-glucuronidase. GAMG is widely used in the pharmaceutical and food industries due to its stronger physiological functions, higher biological activity, more favorable sweetness, and lower caloric value as compared with GL. The recombinant Pichia pastoris (r-PGUS-P)designated in this work expressing β-D-glucuronidase, was used as a whole-cell biocatalyst catalyzing GL to GAMG in non-aqueous solvents systems. The results showed that r-PGUS-P gave the highest yield of GAMG in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6)/water(28,vol)biphasic system. The optimal conditions of this reaction were determined as follows:optimum pH, substrate concentration, temperature and cell content were 5.4, 6.0 mmol·L-1, 45, and 8.0 g·L-1, respectively. Under these optimized conditions, 69.6% yield of GAMG and 67.2% of the chemical bond selectivity was achieved after 58 h reaction time, increase by 12.4% and 12.61%, respectively against aqueous phase.  Simultaneously, the ionic liquid BMIMPF6 alsoremained at higher recovery percentage of about 93.47% during repeated use for 7 reaction cycles. Especially, product GAMG and byproduct glycyrrhetinic acid (GA)got separated in biphasic system automatically that brought convenience for the separation and purification of GAMG.

    催化、动力学与反应器
    Platinum-tin catalysts for dehydrogenation of mixed low hydrocarbons into isobutene
    WANG Yanzhen, WANG Pengcheng, DUAN Hongling, SONG Chunmin, MENG Yang, DONG Yanli
    2011, 62(11):  3143-3148. 
    Abstract ( 1261 )   PDF (754KB) ( 603 )  
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    Nowadays, most of the isobutene was obtained as a by-product from both thermal and catalytic cracking processes. Due to growing of demand, butane dehydrogenation to produce isobutene is a valuable process in petrochemical industry. Traditionally, high purity isobutane is used as feedstock for producing isobutene, in which purification process is complex and cost high. In this paper the dehydrogenation process using mixed low hydrocarbons as raw material to produce isobutene was studied over Pt-Sn/Al2O3 catalyst, and the effect of Pt content, Pt/Sn atomic ratio and chlorine content on isobutane conversion and isobutene selectivity were investigated. The results show that the conversion increases with Pt content from 0.20% to 0.40%(mass)and decreases when it is larger than 0.40%(mass).The maximum conversion, 35%(vol)even after 8 hours, and the maximum yield of isobutene are obtained at 0.40%(mass)because of smaller particle size and better dispersion of platinum, as shown by TEM results. For the effect of Sn addition, the conversion and the selectivity increase first and then decrease with the Pt/Sn atomic ratio. There is the maximum conversion for the catalyst with Pt/Sn atomic ratio 1∶1, the maximum yield 26% for that with Pt/Sn atomic ratio 2∶3 even after the reaction time of 8 hours. The chlorine content in catalyst was measured by potentiometric titration. The data show that the conversion increases with increase of the chlorine content, while the selectivity declines. There is the best catalyst performance for the catalyst with 0.87%(mass)chlorine.

    Development of observed kinetic model for self-flocculating yeast
    YIN Dongli, LIU Chenguang, LI Fan, GE Xumeng, BAI Fengwu
    2011, 62(11):  3149-3155. 
    Abstract ( 1087 )   PDF (1072KB) ( 435 )  
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    With on-line monitoring size distribution of the self-flocculating yeast with the focused beam reflectance measurement (FBRM)system, the impact of mass transfer limitation was eliminated by increasing stirring speed of the fermentor to reduce the size of yeast flocs, and an intrinsic kinetic model for yeast growth was established. Furthermore, based on the shell mass balance theory, an observed kinetic model was developed and model parameters were determined with experimental data collected under the condition of different substrate concentrations and yeast floc size distributions. The analytical results of yeast flocs kinetic behavior indicated that size distribution should be controlled properly in the tanks-in-series system for continuous ethanol fermentation. Large yeast flocs were preferred for the main tanks where higher sugar concentrations could prevent the occurrence of mass transfer limitation, while small yeast flocs should be used for the rear tanks to maintain yeast flocs viability and fermentability in which sugar depletion significantly increased the risk of mass transfer limitation on yeast flocs. The engineering aspects, such as separation of yeast flocs from the fermentation broth by sedimentation, effective immobilization of yeast flocs within the fermentation system by retention and balancing size distributions.

    Intrinsic kinetics for amination of ethanol to acetonitrile over Co-Ni/γ-Al2O3 catalyst
    ZHANG YuechengZHANG Di ZHAO Jiquan
    2011, 62(11):  3156-3163. 
    Abstract ( 1117 )   PDF (938KB) ( 616 )  
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    A continuous flow fixed bed reactor was used to study the intrinsic kinetics for the amination of ethanol to acetonitrile over Co-Ni/γ-Al2O3 catalyst under atmospheric pressure, at reaction temperature in the range of 613—643 K, and the molar radio of ethanol to ammonia ranging from 1∶2 to 1∶10. The kinetic data were collected in the regime where internal and external particle diffusion resistances were absent by using catalyst in the appropriate average size range,appropriate range of residence time as well as other conditions necessary for plug flow and isothermal behavior in the reactor. Power law models were used to fit the experimental data, and the model parameters were fitted by non-linear regression using MATLAB software. The statistical test results showed that the calculated values based on the model were consistent with the experimental data.

    分离工程
    Influences of ligand density and pore size on BSA adsorption on agarose-based DEAE-ion-exchange resins
    LU Huili, LIN DongqiangYAO Shanjing
    2011, 62(11):  3164-3170. 
    Abstract ( 1605 )   PDF (546KB) ( 618 )  
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    Ion exchange chromatography (IEC)is a common and powerful technique for the purification of proteins. The ligand density and pore size of the resins have significant effects on the separation behaviors of protein. In the present work, three kinds of crossed-linked agarose gel with different agarose concentrations were used as the matrices to represent various pore sizes, and anionic ligand, diethylaminothyl (DEAE), was coupled with different ligand densities. The preparation conditions, including the reaction temperature, time, DEAE concentration and NaOH concentration, were optimized to control the ionic exchange capacity. A series of DEAE resins with different ligand densities and pore sizes were obtained. The adsorption isotherms and kinetics of bovine serum albumin (BSA) were measured on these resins. The saturated adsorption capacity increased with the increasing of ligand densities and the decreasing of pore sizes at the range tested. For the adsorption kinetics, the pore size influenced significantly the effective pore diffusivities. The results demonstrated that both the pore size and ligand density affect the static and dynamic adsorption. The pore size dominates the diffusion and mass transfer of protein, while the ligand density affects the interactions between ligand and protein.

    Mass transfer behavior in extraction system of sec-butyl-acetate-acetic acid-water
    QIU TingHONG Sufen, GUO Chuan, LV Yuanju
    2011, 62(11):  3164-3170. 
    Abstract ( 924 )   PDF (1164KB) ( 570 )  
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    In order to know the mass transfer of an extraction system the mass transfer behavior in the system of sec-butyl-acetate-acetic acid-water was studied. Firstly, the shadowgraph optical technique was used to observe Marangoni convection. It was found that the interfacial cellular convection appeared when acetic acid concentration in aqueous solution reached 4.33 mol·L-1. Secondly, the single drop method was used to determine mass transfer coefficient while solute acetic acid transferring from aqueous solution to drops of sec-butyl acetate under various conditions. The effects of drop formation, acceleration and coalescence on the measurement of single drop mass transfer were considered as total terminal effect in the experiment. The results showed that overall dispersed phase mass transfer coefficient remarkably increased with increasing drop diameter and experimental temperature, but decreased with increasing solute concentration in continuous phase. Finally, the experiment data were fitted with the modified combined film mass transfer coefficient model. This study is important to the design and scale-up of extraction column.

    Thermodynamics and dynamics for adsorption removal of 1,2-dichlorobenzene on adsorbent N
    FAN XiujuZHU JianhuaWU BenchengZHAO Xiangmiao
    2011, 62(11):  3179-3185. 
    Abstract ( 1132 )   PDF (594KB) ( 936 )  
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    The thermodynamics and dynamics of 1,2-dichlorobenzene adsorption on adsorbent N were investigated via the static adsorption experiments. The experimental results demonstrated that the adsorption isotherm of 1,2-dichlorobenzene adsorption on adsorbent N was S type, and Freundlich adsorption equation could describe the adsorption process well. The thermodynamic parameters illustrated that the adsorption was a spontaneous and exothermic process, belonging to physical adsorption. The adsorption dynamics appeared to be pseudo-second order equation. As adsorption temperature increased, adsorption rate constant and initial adsorption rate tended to increase. Based on the above-mentioned results, some guidance may be provided for the adsorption removal of organic chlorides from naphtha.

    Adsorption properties of sulfobetaine-type fluorocarbon surfactant on montmorillonite
    ZHENG JingjingWANG YanlingCHANG YuliZHAO XiutaiWANG Yefei, ZHENG LongweiWANG LijuanMA Li
    2011, 62(11):  3186-3191. 
    Abstract ( 1303 )   PDF (535KB) ( 577 )  
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    Surfactant can be lost by adsorption on clay. So binary flooding does not have a good synergistic effect. The adsorption properties on montmorillonite of sulfobetaine-type fluorocarbon surfactant (FS) were studied by colorimetry. The adsorption conditions, such as alcohols, polyacrylamides (HPAM) of different molecular weights, pH and temperature were studied. The results showed that addition of 10% volume ratio of different types of alcohol, by adding methanol, ethanol, isopropanol and butanol reduced the adsorption amount on montmorillonite of the FS. Octanol, decanol, ethylene, glycol, glycerol increased the adsorption amount on montmorillonite of the FS. Ethanol reduced the adsorption capacity value of the FS by 67.25%, while octanol increased the adsorption capacity value of the FS by 86.76%.  So low molecular weight alcohols could reduce the adsorption amount of the FS on montmorillonite. HPAM could reduce the adsorption capacity on montmorillonite of the FS. As the HPAM concentration and molecular weight increased, FS adsorption on montmorillonite declined. HPAM with molecular weight of 20 million lowered FS adsorption on montmorillonite more obviously than that with molecular weight of 10 million. With the increase of pH, the adsorption capacity on montmorillonite of the FS decreased. FS adsorption on montmorillonite could be increased in acidic environments, but FS adsorption on montmorillonite could be decreased in alkaline environments. As temperature increased, the adsorption capacity on montmorillonite of the FS first increased and then decreased, with the maximum adsorption capacity at 4050. X-ray diffraction (XRD) of montmorillonite treated with the FS indicated that the FS entered the clay, and increased the layer spacing of MMT.

    Static and dynamic adsorption of fluoride using La()-loaded chitosan beads crosslinked with EGDE
    MENG Fanping, LI Yongfu, ZHOU You, DU Xiuping
    2011, 62(11):  3192-3200. 
    Abstract ( 1583 )   PDF (1060KB) ( 644 )  
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    A new absorbent for the removal of fluoride from drinking water was prepared by using lanthanum loaded chitosan beads crosslinked with ethylene glycol diglycidyl ether (EGDE)replacing glutaraldehyde (GLA).Static and dynamic adsorption of fluoride onto absorbents (CEB-La)was investigated, respectively. The effects of various physico-chemical parameters were studied. The results of static experiment showed that the optimal adsorption conditions were pH7. 0 water temperature 50, contact time 60 min, and oscillation frequency 120 r·min-1. Treating the water containing F- of 10 mg·L-1 with CEB-La under this condition, the defluoridation rate was up to 92.9% and the residual concentration of F- was 0.71 mg·L-1, lower than 1.0 mg·L-1. Furthermore, the adsorption isotherm could be described by the Langmuir and Freundlich models and the maximum adsorption capacity for F- was 25.7 mg·g-1. Sorption dynamics study revealed that the pseudo-second-order equation was suitable to describe the kinetics process of fluoride ions sorption onto the adsorbent. The used adsorbents could be regenerated by chelating with lanthanum after soaking in 0.5 mol·L-1 of sodium hydroxide for 6 h. The removal efficiencies of F- were related to the co-existing anions. In particular, the presence of CO2 -3 and HCO-3 led to a markedly decreased adsorption capacity of CEB-La for F-. The results of dynamic experiment demonstrated that CEB-La was suitable for treating drinking water containing F- of 215 mg· L-1 when the volumetric flow rate was 3 ml·min-1. Column kinetics were described by the Thomas model and the dynamic adsorption capacity was 3.67 mg·g-1. Therefore, the absorbent is easy to regenerate, of low-cost, and has superior defluoridation properties, showing that it is a potential material for F- removal in practice.

    Adsorption characteristics of uranium by Saccharomyces cerevisiae by chemical modification
    PENG Guowen, DING Dexin, HU Nan, YANG Yushan, WANG Xiaoliang
    2011, 62(11):  3201-3206. 
    Abstract ( 1715 )   PDF (963KB) ( 937 )  
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    Modified Saccharomyces cerevisiae (MSC)was prepared from Saccharomyces cerevisiae (SC)by cystine modification and formaldehyde as crosslinker, and was immobilized by alginate sodium and glut. FTIR was used to characterize MSC and SC, and the effects of pH value and time on uranium adsorption over MSC and SC were investigated. It was found that there were many functional groups on the cell wall of MSC for adsorbing uranium. The optimal conditions for uranium adsorption were as follows: pH of the solution 6.0; the adsorption time for MSC and SC was 1.8 h and 1.5 h, respectively. The adsorption kinetics and isotherm models were proposed for adsorption of uranium on MSC and SC by fitting experimental data. The pseudo-second-order mode was better for both MSC and SC, their correlation coefficient better than 0.99(R2>0.99), and Langmuir and Freundlich models were better isotherm models, indicating that the adsorption mode of uranium adsorption on MSC and SC was a combination of monolayer cover and multilayer adsorption. The capability of adsorption for MSC was 6.5 times that for SC, and indicated that MSC had potential as bioadsorbent.

    分离工程
    Realizating chiral separation of enantiomers of glutamic acid with novel surface-molecular imprinting technique
    GUO Jianfeng, GAO Baojiao, ZHANG Zhengguo
    2011, 62(11):  3207-3214. 
    Abstract ( 1169 )   PDF (729KB) ( 515 )  
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    Poly 4-vinyl pyridine/SiO2 (P4VP/SiO2), a grafted functional particles, was prepared by grafting 4-vinyl pyridine (4VP)on micro-sized silica gel particles with the “graft from” method, using 3-methacryloxypropyl trimethoxysilane (MPS)as coupling agent. Subsequently, by using the novel surface-molecular imprinting technique, the L-Glu molecule-imprinted material MIP-P4VP/SiO2 was prepared by imprinting towards the grafted P4VP with L-Glu, one enantiomer of glutamic acid (Glu), as template molecule and 1,6-dibromohexane as crosslinking agent. The recognition characteristics of MIP-P4VP/SiO2 for L-Glu was studied by both static method and dynamic method in which D-Glu was used as a contrast compound. The separation ability of MIP-P4VP/SiO2 towards L-Glu and D-Glu in the racemic solution was examined. The experiment results showed that MIP-P4VP/SiO2 had obvious recognition selectivity and fine binding affinity for L-Glu, and the selectivity coefficient was equal to 3.38 with respect to D-Glu, displaying the fine separation property for the enantiomers of glutamic acid. Besides, MIP-P4VP/SiO2 had excellent elution property with diluted aqueous solution of NaOH as eluent, the desorption ratios of L-Glu could reach 99.53% in 12 BV. Moreover, this material showed effective separation ability of repeated use for more than ten times.

    表面与界面工程
    Molecular dynamics simulation of dodecyl-β-D-glucoside surfactant monolayer
    YU WeizhaoYU LijunZHANG JunHU SongqingTI YangWANG Pan
    2011, 62(11):  3215-3221. 
    Abstract ( 1430 )   PDF (1663KB) ( 489 )  
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    Interfacial self-assembly structure of surfactants is one of the key properties for its application. Taking account of limitation of experimental techniques in characterization of such structures, molecular dynamics simulation has emerged to be one of the powerful tools for investigating surfactant interfacial processes. In this paper, the structural and dynamic properties of mono-layer membrane consisting of non-ionic surfactant dodecyl-β-D-glucoside at various concentrations on interfaces between aqueous and gaseous phases were studied with molecular dynamic simulation. The structure and stability of the mono-layer membrane were investigated with the density distribution and mean square displacement curves of surfactant molecules at different concentrations, and interface formation energy of different surfactant self-assembly systems. And the arrangement of alkyl chains in the membrane of these surfactant systems was also compared in terms of the average order parameters of C atoms in alkyl chains of the surfactant molecules. Simulation results showed that with the increase of surfactant concentration, the thickness of the membrane increased, the arrangement of alkyl chains on the interface became more orderly, and the migration ability of the membrane was reduced to achieve improved stability.

    Oxygen evolution properties of titanium-based IrO2+SnO2 electrode and application in electrolytic synthesis of succinic acid
    MA Chunan, QIU Zhijun, ZHAO Fengming,ZHU Xiushan, CHU Youqun
    2011, 62(11):  3222-3227. 
    Abstract ( 1224 )   PDF (1157KB) ( 536 )  
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    The dimensionally stable anode(DSA)has been developing quickly in recent years. The IrO2+SnO2/Sb2O3+SnO2/Ti, IrO2+Ta2O5/Sb2O3+SnO2/Ti and IrO2+SnO2/Ti coated electrodes were prepared by the thermal decomposition method. The properties of the coated electrodes for oxygen evolution were studied by linear sweep voltammetry, electrochemical impedance spectroscopy and accelerated corrosion test. Pb and its alloy electrodes were also used in contrast experiment. Distribution of chemical elements and surface topography were observed by EDX and SEM. The effects of electrolytic result were investigated with the coated electrodes, Pb and its alloy electrodes as anode in electrolytic synthesis of succinic acid. The results showed that the cell voltage reduced by 0.5—0.7 V and current consumption of electrolysis decreased by almost 10% when the coated electrodes instead of Pb and its alloy electrodes were used in the electrolytic process. Based on the comparison of three coated electrodes, the SnO2-Sb2O3 interlayer could improve the properties of the coated electrodes for oxygen evolution and the service life of the coated electrodes in H2SO4 solution. The IrO2+SnO2/Sb2O3+SnO2/Ti electrode displayed favorable performance for oxygen evolution and the working life exceeded 1456 days as the SnO2 replaced Ta2O5 in the active coating of electrode. Although cell voltage and current consumption of electrolysis were a little bit higher, IrO2+SnO2 coated electrode was more cost effective because of replacement of noble metal in active coating.

    生物化学工程与技术
    Mechanism and effect of acid stress on glutathione biosynthesis by Candida utilis
    DONG Yingying, WEI Gongyuan, ZHANG Junli, CHEN Xuedong
    2011, 62(11):  3228-3235. 
    Abstract ( 1359 )   PDF (487KB) ( 576 )  
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    The effect of pH on glutathione production was investigated in batch culture of Candida utilis SZU 07-01 in this study, pH3.5 and pH1.5 were determined as mild acid stress and severe acid stress conditions, respectively, based on analyzing and comparing the process parameters. Optimal time of 6 h and 2 h for mild acid stress of pH3. 5 and severe acid stress of pH1. 5 were then chosen for glutathione overproduction, respectively, during continuous culture of C.utilis SZU 07-01 in a chemostat.  Furthermore, C.utilis SZU 07-01 was cultured under batch culture with glucose feeding and acid stress, it was found that mild acid stress for 6 h was more advantageous to glutathione overproduction than severe acid stress for 2 h and no acid stress. In the end, the mechanisms of glutathione overproduction by mild acid stress were quantitatively interpreted by comparison of parameters obtained from batch fermentation kinetics, intracellular cofactors as NADH and ATP, together with the distribution of flux on key metabolites within glutathione biosynthesis.

    Freeze-drying process and characteristic configuration of coenzyme A
    YIN Shuangqing,JI Min,YAO Risheng
    2011, 62(11):  3236-3241. 
    Abstract ( 1084 )   PDF (1780KB) ( 433 )  
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    The stability of coenzyme A solution was studied. It was found that the content of coenzyme A in the solution decreased with increasing storage time and increasing temperaturewhile it remained relatively constant for 24 h under conditions of temperature 15 and pH value 4.5. For this reasonthe freeze-drying technology was introduced.  Using freeze-drying dosage-form and moisture content as qualitative indicesthe return warming freeze-drying was proven superior to traditional ladder warming freeze-drying with respect of the product quality of coenzyme A. The characteristics and configuration of coenzyme A obtained from an ordinary drying process and different freeze-drying processes were further analyzed by optical image and X-ray diffraction. The findings demonstrated that the ladder warming freeze-drying process was better than the ordinary drying process with respect to the formation of the crystal structure of coenzyme Awhile the return warming freeze-drying process further outweighed the ladder warming freeze-drying process.  Moreoveran optimized 16 h return warming freeze-drying process was finally proposed to obtain coenzyme A with high-purity(95%),high crystallinity and good stabilitybased on the research on the return warming freeze-drying process and also the acceleration stability test.

    能源和环境工程
    Energy-saving analysis of solution regeneration in heat-source tower based on recovery of air energy
    WEN XiantaiLIANG CaihuaLIU ChengxingZHANG Xiaosong
    2011, 62(11):  3242-3247. 
    Abstract ( 1262 )   PDF (391KB) ( 641 )  
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    The heat-source tower heat pump system was analyzed and the problem of solution regeneration in winter was presented. Considering the characteristics of low moisture absorption of the solution, a new regeneration design of heat-source tower based on recovery of air energy was proposed, and theoretical analysis of regeneration performance was conducted. Mathematical models of the components, including compressor, heat exchanger, expansion valve and regenerator of solution were built and the whole regenerative system was simulated. The results showed that with the increase of inlet solution temperature in the condenser from 18 to 28, the regeneration rate increased linearly from 17.7 kg·h-1 to 26.7 kg·h-1, the COP of the system kept constant at 4.3, the latent heat percentage increased from 68.3% to 82%, and the COP of latent heat increased from 2.8 to 3.5. Compared with the traditional regeneration system, this system consumed less energy, and had higher energy efficiency, promising huge energy-saving potential.

    Performance of continuous hydrogen production in annular fiber-illuminating biofilm reactor
    ZHANG Chuan LIAO QiangZHU XunWANG Yongzhong
    2011, 62(11):  3248-3255. 
    Abstract ( 1472 )   PDF (734KB) ( 587 )  
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    To solve the problem of insufficient light supply within cell-immobilized bioreactor, a new type of annular fiber-illuminating biofilm reactor(AFIBR)was developed for photo-H2 production by indigenous photosynthetic bacteria Rhodopseudomonas palustris CQK 01 using glucose as the sole carbon source. A side-glowing optical fiber(SOF)with desired surface light intensity and uniform light distribution was inserted into a sealed glass vessel as internal light source of AFIBR and photosynthetic bacterial cells were successfully attached onto the surface of SOF to form a steady biofilm within bioreactor at the start-up stage of bioreactor. A detail investigation of the continuous hydrogen production performance of AFIBR was then carried out under different light wavelength, light intensity, inlet substrate concentration and flow rate. The results showed that AFIBR exhibited excellent performance on both hydrogen production and light energy conversion. A high hydrogen production rate of 0. 83 mmol·(g cell-1·h-1 and excellent light conversion efficiency of 47.9% were attained under the operational conditions of monochromatic light illumination at 530 nm, light intensity of 4.15 W·m-2, inlet substrate concentration of 10 g·L-1 and flow rate of 100 ml·h-1. The results revealed also that proper emission spectrum of light source, even light intensity distribution within cell-immobilized zone within bioreactor and enhanced mass transfer operation were efficient measures to improve the performance of AFIBR. So, further research on photobiological reactor may be necessary for practical hydrogen production.

    Pretreatment of corncob residues in organic solvent and its effect on enzymatic digestibility
    YUE Jun, YAO Lan, ZHAO Jian, LI Xuezhi, QU Yinbo
    2011, 62(11):  3256-3262. 
    Abstract ( 1557 )   PDF (887KB) ( 843 )  
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    Solid residues from dilute acid pretreatment process of corncob may be used to produce liquor fuels and chemicals by bioconversion because of its high cellulose content,but its high lignin content leads to decrease of cellulose enzymolysis efficiency. The digestibility of enzyme can be improved by removal of lignin in lignocelluloses materials with some organic solvent. In this paper, pretreatment of corncob residues was carried out in ethanol solution and effect of process parameters (pretreatment temperature and time,ethanol concentration,ratio of solid to liquid)on chemical components and enzymatic digestibility was studied. The results showed lignin of 53. 26% could be removed under pretreatment conditions of ethanol concentration 50%, 210℃, ratio of solid to liquid 1∶8 and 60 min, and the conversion of cellulose to glucose increased from 69.84% to 84.42%. Compared with corncob residues, the pretreatment process was more effective for corn stover and corncob to remove lignin and increase enzymolysis efficiency of cellulose.

    Distribution of PAHs between soils and pine needles collected from typical areas of Xinjiang
    LI Weiwei, MA Xindong, RAN Dan, WANG Zhen, LU Jianjiang
    2011, 62(11):  3263-3268. 
    Abstract ( 1399 )   PDF (591KB) ( 443 )  
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    Concentrations of polycyclic aromatic hydrocarbons (PAHs)in soils and pine needles collected from typical areas of Xinjiang (Shihezi, Beitun and Kanas)were measured to investigate their distribution between the two environmental media. The concentrations of PAHs in soils and pine needles samples from the three regions were lower than that from other typical regions. The proportion of low molecular weight PAHs was higher and that of high molecular weight species was lower for Shihezi’s sample than that for Kanas’s one. The ring distribution of PAHs in samples from the three regions was a result of “local atmospheric distillation”.Significant log/log-linear relationship was observed between the sub-cooled liquid vapor pressure and the soil/needle quotient, which was similar to one between the gas/solid partition coefficient and the sub-cooled liquid vapor pressure of atmospheric PAHs. These results indicated that the soil/needle quotient can be considered as a “mirror image” of the gas/solid partition coefficient.

    能源和环境工程
    Character of turbulent contact absorber in treating low concentration CO2 flue gas
    ZHOU Xiang,LEI Cheng,Tim C. Keener, SONG Cunyi
    2011, 62(11):  3269-3275. 
    Abstract ( 1228 )   PDF (646KB) ( 724 )  
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    CO2 concentration in the atmosphere is critical for global warming.  The emission from power station is one of the biggest CO2 point sources in the world. In all kinds of CO2 capture methods, the post-combustion adsorption is the most potential one for commercial application in existed power plants. In contrast with packing tower which is investigated by many researchers, the TCA(turbulent contact absorbercan employ higher gas velocity to reduce systems occupancy area. In order to better understand TCA capturing CO2 system, a series of experiments were conducted under different operating conditions using pure water and different concentration NaOH solution at low CO2 concentration(7%14%flue gas. The TCA column has 0.13 m diameter and 1.5 m height, and is operated at counter-current mode and flue gas was introduced from a furnaces flue gas system. The effects of the gas distributor, static packing uniformity, inlet CO2 concentration, gas residence time, L/G(liquid-gas ratio), and concentration of solvent were also examined. And the production of the overall mass transfer coefficient and the interfacial area in the unit volume Kga were calculated for NaOH solution. Higher heights of Raschig rings as gas distributor as well as higher residence time and L/G, higher CO2 removal efficiency, whereas uniformity of static packing(10 mm diameter polypropylene ballas well as increase of inlet CO2 concentration has a little effect on removal efficiency at sufficient turbulence condition.  The gas film resistance is not significant for H2O-CO2 system in TCA, but gas holdup decreases with increase of L/G.  Reactions between NaOH and CO2 can reduce liquid film resistance and increase the removal efficiency. 35.3%66.7% removal efficiencies and 1.3×10-7)—(1.8×10-7 kmol·m-3·s-1·Pa-1 Kga are achieved with 1 mol·L-1 NaOH and L/G 1224 L·m-3. The gas film resistance is not important when NaOH concentration<1 mol·L-1, but when NaOH concentration >1 mol·L-1, it becomes significant. In contrast to liquid film resistance,removal efficiency can go up to 66.7% CO2 at 1 mol·L-1 NaOH, 0.18 m Raschig rings gas distributor, 0.4 m static polypropylene balls packing and 24 L·m-3 liquid gas ratio. At last, a comparison of operating conditions between different types of absorbers under similar diameter size was made.

    材料化学工程与纳米技术
    Synthesis and electrochemical properties of MnO2 nanomaterials from spent LiMn2O4 batteries
    YANG Zeheng, NI Yulong, MEI Zhousheng, WANG Qiang, ZHANG Weixin
    2011, 62(11):  3276-3281. 
    Abstract ( 1165 )   PDF (1286KB) ( 661 )  
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    λ-MnO2 nanoparticles and β-MnO2 nanorods were successfully prepared from spent LiMn2O4 cathode materials by controlling appropriate leaching conditions in this study. Their electrochemical properties were investigated as electrode materials for primary cells and supercapacitors. The composition, morphology and electrochemical properties of the obtained samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), constant current charge-discharge and cyclic voltammetry measurements. The results indicated that λ-MnO2 nanoparticles could be prepared at ambient temperature and pressure, with 0.5 mol·L-1 H2SO4 leaching the spent LiMn2O4 for 3 h, and β-MnO2 nanorods could be synthesized under hydrothermal conditions of 140℃, with 2 mol·L-1 H2SO4 leaching the spent LiMn2O4 for 24 h. The λ-MnO2 and β-MnO2 samples delivered discharge capacities of 142 mA·h·g-1

    Medium-resistance performance of PPTA-pulp-reinforced EPDM composites
    LIU XiaogangLI JinchunYOU Xiulan
    2011, 62(11):  3282-3287. 
    Abstract ( 1643 )   PDF (400KB) ( 613 )  
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    Poly-phenylene terephthalamide (PPTA-pulp)-reinforced ethylene propylene diene elastomer (EPDM)composites were prepared in an open mixer. The effects of fiber content on medium-resistance performance and heat aging resistance of the composites were investigated. With swelling behavior of the composites studied by the weighing method, the experimental curves were fitted by computer. The swelling dynamic rate equations were established. Experimental results showed that medium-resistance performance, and heat aging resistance of the composites increased greatly by adding PPTA-pulp. When the content of the fiber was up to 25% (mass), the composites showed the best performance. The swelling behavior of EPDM/PPTA-pulp composite could be described by the Voigt parallel dashpot-spring model.Basic equation was not changed, but equilibrium swelling ratio and relaxation time of chain movement were changed on the addition of fiber. Both swelling ratio and relaxation time decreased with increasing fiber content.

    Preparation of macroporous GMA-DVB resins aminated by polyethylene polyamines and their adsorption of metallic ions
    ZHOU Yun, YAN Xin, ZHOU Liqing
    2011, 62(11):  3288-3294. 
    Abstract ( 1637 )   PDF (2023KB) ( 736 )  
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    Macroporous glycidyl methacrylate-divinylbenzene copolymer resins were synthesized by suspension polymerization using toluene-n-heptane mixture as a porogen, and their aminated resins were prepared by the reaction of epoxy groups in the copolymer resins with polyethylene polyamines. The measurements of exchange capacity, pore volume and porosity showed that amino content, pore volume and porosity of the aminated resins decreased as the contents of divinylbenzene increased, and that pore volume and porosity of the aminated resins increased with increasing amount of the porogen. The results of the adsorption of Cu2+, Co2+, Ni2+ and Zn2+ on the aminated resins showed that the aminated resins had good adsorption capability of the four ions and the adsorption amount of Cu2+ was much higher than those of the other three ions. The adsorption rates of the four metal ions on the aminated resins depended on amination with polyethylene polyamines and the contents of divinylbenzene and the porogen. The adsorption kinetics can be described by pseudo second-order rate equation.

    材料化学工程与纳米技术
    Synthesis of adamantane-containing cationic surfactants
    CAI Lu GUO JianweiLIU SaGUAN NianyunZHU LejieCUI YingdeSUN Baoxing
    2011, 62(11):  3295-3300. 
    Abstract ( 1583 )   PDF (409KB) ( 513 )  
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    Eight halogen quaternary ammonium cationic surfactants containing adamantane structure were successfully synthesized through quaterisation of the intermediate compound-N,N-dimethyl tertiary amine using halogen quaternary ammonium reagents. N-(1-adamantyl)-N,N-dimethylamine was synthesized through the Eschweiler-Clarke methylation reaction in which 1-adamantine and formaldehyde with excess formic acid were used as raw materials. The yields of the eight products were 90%, 85%, 75%61%44%54%87%, 45% respectively. The structures of all these compounds were confirmed by elemental analysis, IR, and 1H NMR. Surface tensions of these eight compoundsaqueous solutions with concentration of 0.1% and 1% were measured. The results showed that the surface tensions of these aqueous solutions decreased to different degrees compared with pure water. It was also found that the difference of surface activity among similar structure compounds with different anions (halide ions)was not significant. However, surface activity increased when the carbon chain lengths of the quaternary ammonium reagents increased.

    Preparation of nano-sized iron oxide red using δ-FeOOH as seed and iron as raw material in liquid phase at low temperature
    ZHAO Liyan,LU Bin,LIU Hui,WEI Yu
    2011, 62(11):  3301-3305. 
    Abstract ( 1366 )   PDF (860KB) ( 972 )  
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     Uniform pseudocube nano-iron oxide red (hematite)particles was prepared in the liquid phase by using δ-FeOOH as seed and iron as raw material at low temperature. The effects of such factors as initial pH of reaction, concentration of catalyst, reaction time on the preparation of these hematite particles were investigated. The product was characterized by XRD, IR, FESEM. The results showed that pure pseudocube hematite particles could be prepared under the experimental conditions of solution initial pH 7, β=0.09β=Fe2+/[δ-FeOOH]), air oxidation temperature and time of 100 and 48 h respectively. The product crystallized integrally with particle diameter 90100 nm, and its color was brightly red. This is a new method to prepare high-purity nano-iron oxide red with the characteristics of simple operation, non-pollution and low cost.