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Table of Content
05 December 2014, Volume 65 Issue 12
    CIESC Journal(HUAGONG XUEBAO)Vol.65 No.12 May 2014
    2014, 65(12):  0-0. 
    Abstract ( 183 )   PDF (66518KB) ( 259 )  
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    Progress of computability of multi-scale interface problems in gas-liquid two-phase flow
    ZHANG Wenwei, KE Peng, YANG Chunxin, ZHOU Chenglong
    2014, 65(12):  4645-4654.  doi:10.3969/j.issn.0438-1157.2014.12.001
    Abstract ( 326 )   PDF (7328KB) ( 956 )  
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    Gas-liquid two-phase flow has complex interface structures with a wide range of spatial scales in the transient time. The multi-scale interface problems are related to various fields, such as chemical engineering, nuclear safety, and so on. Computability of these problems is one of the research priorities. This paper analyzes basic models dealing with the discontinuity of phase interfaces in the Eulerian reference frame, and describes the influence relationship between turbulent simulation methods and interfaces. The difficulties of computability are analyzed for two types of multi-scale problems: scale distribution of interfaces in dispersed flows and cross-scale of interfaces in mixed flow. Two factors including the scale for computational grid and the loss of geometry and physical boundaries are concluded. The computing methods and typical applications in cross-scale of interfaces in mixed flow are summarized. The strategies and trends of the research on those multi-scale problems are proposed, providing useful guides for the research.
    Influence of pinch point temperature difference and fluid properties on trans-critical organic Rankine cycle
    YU Chao, XU Jinliang, MIAO Zheng, YANG Xufei
    2014, 65(12):  4655-4663.  doi:10.3969/j.issn.0438-1157.2014.12.002
    Abstract ( 362 )   PDF (687KB) ( 263 )  
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    Thermal performance values of 41 working fluids in a trans-critical organic Rankine cycle (ORC) driven by waste heat flue gas of 473.15 K were calculated by means of a theoretical model in which the inlet and outlet temperatures of flue gas were fixed and therefore the thermal efficiency and net work output were unified into one parameter as long as the heat absorbed was given. The influences of pinch point temperature difference (PPTD) in the evaporator and working fluid properties on cycle performance were analyzed. Calculation results showed that for fluids with critical temperature Tc<Tgas,out, and fluids with Tc>0.88Tgas,in, Tc had dominant influence on thermal efficiency. For fluids with Tc between Tgas,out and 0.88Tgas,in, fluid dryness had significant influence on cycle performance, and wet fluids outperformed dry fluids apparently. Wet fluids with Tc between Tgas,out and 0.88Tgas,in exhibited the highest thermal efficiency. For fluids with Tc>0.88Tgas,in, PPTD might lie either inside the evaporator or at the outlet. Thermal performance values of the cycle with PPTD inside the evaporator outperformed that with PPTD at the outlet. Application of such conclusions was confirmed through sensitivity analysis for flue gas inlet and outlet temperatures.
    Determination and correlation of solubilities of lithium chloride and sodium chloride in NMP
    LI Baichun, DU Dongxue, ZHANG Wenlin, MENG Kai
    2014, 65(12):  4664-4668.  doi:10.3969/j.issn.0438-1157.2014.12.003
    Abstract ( 444 )   PDF (469KB) ( 599 )  
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    In order to recover the additive lithium chloride in the polyphenylene sulfide production, the disolution of lithium chloride and sodium chloride in solvent N-methyl pyrrolidone (NMP) was studied. By using laser diffraction assistance method, solubility data of lithium chloride and sodium chloride in NMP were measured between 297.95 K and 364.75 K. Empirical formula, λh equation and improved NRTL equation were used to correlate the solubility data of lithium chloride in NMP. The results show that the solubility of lithium chloride increases with temperature while that of sodium chloride almost keeps unchanged. The improved NRTL equation can predict the solubility data well and the relative average error is 0.41%. Thus the K-NRTL equation is most suitable for description of solid-liquid equilibrium of lithium chloride in NMP at high temperature.
    Movement characteristics of droplets and demisting efficiency of mist eliminator
    HAO Yajie, LIU Jiayu, YUAN Zhulin, YANG Linjun
    2014, 65(12):  4669-4677.  doi:10.3969/j.issn.0438-1157.2014.12.004
    Abstract ( 248 )   PDF (2164KB) ( 405 )  
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    In order to improve demisting efficiency of baffle demisters for different droplets and reduce droplet entrainment in the wet flue gas desulfurization (WFGD) system, the computational fluid dynamics (CFD) method was used to simulate numerically the two phase flow of gas and liquid in baffle demister in the WFGD system. By changing the structural parameters and operating parameters of the baffle demister, such as plate spacing, blade-shape and gas-velocity, demisting efficiency and droplets' separation efficiency of different sizes were investigated. The movement behavior and deposition of droplets with different sizes were obtained. The removal efficiency of droplets less than 10 μm would show irregular fluctuations if flow rate was increasing, but almost remained unchanged with increasing plate spacing. In that case removal efficiency was not affected by blade shape. The removal efficiency of droplets over 16.3 μm would increase with increasing flow rate, and decreased significantly with increasing plate spacing. The demisting efficiency of trapezoidal plates was greater than that of triangle plates with plate spacing of 38 mm, and the difference in demisting performance for these two plates was not significant in smaller plate spacing. Removal of the droplets less than 20 μm required higher airflow uniformity at lower gas flow rate. Increased airflow disturbance was in favor of small droplets' collision-coalescence when gas flow rate was less than 3 m·s-1, and increased airflow disturbance was not conducive to small droplets' collision-coalescence when gas flow rate was over 3 m·s-1.
    Visualization experiments of bubble growth and detachment on catalytic surface in a microchannel
    YE Dingding, XIANG Wei, ZHU Xun, LI Jun, LIAO Qiang
    2014, 65(12):  4678-4683.  doi:10.3969/j.issn.0438-1157.2014.12.005
    Abstract ( 262 )   PDF (1799KB) ( 304 )  
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    A rectangular microchannel was fabricated with polydimethylsiloxane (PDMS) material and MnO2 catalysts were deposited on the wall of the microchannel. The growth and detachment process of oxygen bubbles generated by the catalytic reaction of H2O2 solution were recorded by a high speed camera. The effects of reactant concentration and flow rate on bubble growth rate and detachment diameter were also analyzed. The growth and detachment process of bubbles generated on the catalytic surface in the microchannel occurred periodically. Moreover, the bubble growth consisted of two processes, the initial fast growth process and the later slow growth process. Before 3 s, the generated bubbles were in a fast growth period, and reaction kinetics dominated the process. However, after 3s, reaction rate was controlled by diffusion, resulting in the fact that bubble growth rate increased with increasing reactant concentration. In addition, bubble detachment diameter was slightly affected by reactant concentration, while it was significantly affected by reactant flow rate and dropped linearly as Reynolds number increased.
    Gas-liquid flow and mass transfer characteristics of gas-inducing reactor with CFD simulation
    HONG Housheng, ZHANG Zhiqiang, CAI Zijin, YAN Xu, GU Chengzhen
    2014, 65(12):  4684-4691.  doi:10.3969/j.issn.0438-1157.2014.12.006
    Abstract ( 202 )   PDF (2770KB) ( 226 )  
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    By coupling Higbie gas-liquid mass transfer model, Euler three-dimensional transient gas-liquid flow model was established for a six impeller self-inducing reactor with gas distributor. The model was used to simulate the flow field, gas holdup, gas-inducing rate and dissolved oxygen transfer of the gas-liquid mixing process with CFX software. The flow characteristics of the reactor, gas-liquid dispersion performance, gas induction and gas-liquid mass transfer properties were obtained. The analysis on flow pattern characteristics and dissolved oxygen transfer performance at horizontal and vertical positions of the reactor were made, comparing and analyzing the prediction of gas holdup and gas-inducing rate based on experimental data and empirical correlations. Six impeller rotor and gas distributor could obtain uniform gas-liquid mixing. Deviations of gas hold-up and gas-inducing rate predictions from experimental values were 5.2% and 17.6% respectively. Dissolved oxygen transfer and mixing performance near the wall at the bottom of the reactor was bad.
    Modeling of wet-gas flow through horizontal Venturi based on void fraction
    YU Peining, XU Ying, ZHANG Tao, WEI Jing, BA Xili, LI Jing, QIN Zigeng
    2014, 65(12):  4692-4698.  doi:10.3969/j.issn.0438-1157.2014.12.007
    Abstract ( 261 )   PDF (878KB) ( 231 )  
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    In this study, by using the two-phase hydrokinetic theory, a theoretical model for gas-liquid annular and stratified flows through a horizontal Venturi meter was developed. The momentum equation for the gas phase was solved in the axial direction, by considering the factors including void fraction, friction between two phases and entrainment of droplets in the gas core. By modifying the void fraction model proposed by Lockhart and Martinelli, a void fraction model for the convergent tube was developed. Using the modified void fraction model, the distribution of wet gas static pressure between two pressure tappings of the venture meter was simulated. For the sake of checking the validity of this model, wet gas flow experiments were performed by using the standard venture meters with diameter ratio of 0.55 and 0.4 in the flow laboratory of Tianjin University. The predicted points of the modified model were within error band of ±15%. As the model was developed more based on dynamics characteristics of wet gas flow, it could form the basis for further establishing a general flow measurement model of wet gas.
    Numerical simulation of gas-solid flow characteristics in multi-jet cyclone
    ZHAO Yan, XU Weiwei, WANG Jianjun, WANG Rui, GAO Guangcai, JIN Youhai
    2014, 65(12):  4699-4708.  doi:10.3969/j.issn.0438-1157.2014.12.008
    Abstract ( 191 )   PDF (3456KB) ( 304 )  
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    Based on Fluent 6.3.26, the gas-solids two-phase flow behavior and details of multi-jet cyclone with swirling based on nozzles, was simulated and analyzed with the Reynolds stress model (RSM) and discrete particle model (DPM). Compared with conventional cyclones, peak value of tangential velocity and average value of free-vortex reached 160 m·s-1 and 130 m·s-1 respectively, generating higher flow rotation intensity. Volume rates of downward flow kept declining along the central line, particularly in the stabilization region, inducing more chances for particles being entrained by inner upward flow with lower collection efficiency. Local roof wall-jet and circulating flow nearby the inlet of the hopper were typical secondary flows of multi-jet cyclone. Gross pressure loss of the separator was 27.43 kPa, consisting of outer swirl flow 4.57 kPa (21.8%), inner swirl flow 5.76 kPa (27.6%) in the nozzles region, and outer swirl flow 5.85 kPa (27.6%), inner swirl flow 4.01 kPa (18.9%) in the stabilization region. Particles with diameters larger than 10 μm could be collected completely with cut-diameter 1.6 μm, making it suitable for industrial application. Analyzing with the particle mechanical model in this paper, the critical diameter of particle that can be separated was 1—2 μm and particle concentration for particles large than 3 μm in the vortex finder was less than 0.15 g·m-3.
    Drop size distribution and specific surface area in spray tower
    ZHU Jie, WU Zhenyuan, YE Shichao, LIU Zhenhua, YANG Yunfeng, BAI Jie
    2014, 65(12):  4709-4715.  doi:10.3969/j.issn.0438-1157.2014.12.009
    Abstract ( 237 )   PDF (2167KB) ( 611 )  
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    The drop size distribution in a spray tower was obtained by means of the photographic technique with air and water as the experimental media. The effects of spray flux and superficial gas velocity on Sauter mean diameter (SMD) of droplets at different heights of the absorption zone were investigated. The drop size distribution was analyzed theoretically. Dense droplets assembled at the top of the tower; on the contrary, droplets became sparse at the bottom. Small and uniform droplets could be formed in the falling process. With increasing spray flux, the SMD of droplets increased at the top of the tower, while decreased at the middle and lower zones. Average droplet diameter decreased with increasing superficial gas velocity. Theoretically, the decrease of droplet size was mainly accounted for by collision and breakup among droplets, which was primarily caused by diversity of droplet diameters. Dimensionless correlation of SMD was proposed, and the calculation results were in good agreement with the actual data. The specific surface area of spray tower with collision and breakup among droplets was about 70% larger than that without collision and breakup.
    Heat transfer characteristics of MSW and its typical components in rotary kiln at different pyrolysis stages
    WANG Huan, YIN Lijie, CHEN Dezhen, MA Xiaobo, HE Pinjing
    2014, 65(12):  4716-4725.  doi:10.3969/j.issn.0438-1157.2014.12.010
    Abstract ( 213 )   PDF (874KB) ( 275 )  
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    Heat transfer characteristics of typical components of municipal solid wastes (MSWs), including paper, fabric and biomass and MSW without inert components during the pyrolysis process were experimentally studied in an externally heated rotary-kiln pyrolyser at different heating rates and different rotational speeds. According to the data of thermogravimetric analysis at similar heating rate, the pyrolysis process could be divided into four stages: moisture evaporation stage, pre-pyrolysis stage, violent pyrolysis stage and ending stage. In the moisture evaporation stage, apparent heat transfer coefficients of typical MSWs components and MSW without inert components were the highest but decreased rapidly till reaching a minimum. In the pre-pyrolysis stage, apparent heat transfer coefficients of typical MSWs components and MSW without inert components changed little, having the characteristics of lowest steady heat transfer coefficient. Then in the violent pyrolysis stage, apparent heat transfer coefficients of typical MSWs components and MSW without inert components increased gradually as temperature rose. When the pyrolysis proceeded to the ending stage, the above mentioned apparent heat transfer coefficients decreased again. Apparent heat transfer coefficients also varied with rotational speed and heating rate of the rotary kiln and the effects of rotational speed and heating rate on different materials were different. In general, under the condition of low heating rate (22±2)℃·min-1, higher rotational speeds of the rotary kiln had inhibitory effects on heat transfer at the end of moisture evaporation stage and in the pre-pyrolysis stage; while under the condition of high heating rate (32±2)℃·min-1, higher apparent heat transfer coefficients were obtained, and the total pyrolysis time was shortened. Except for biomass, the higher the rotational speed, the higher the apparent heat transfer coefficients in the corresponding pyrolysis stage and the pre-pyrolysis stage would disappear when rotational speed was up to 3 r·min-1. Those results could provide useful guides for the design and use of rotary kiln pyrolysis reactors.
    Heat transfer performance of liquid flow in multi-port micro-channel tubes
    LI Minxia, YU Wenfang, SUN Han, DAI Baomin, DANG Chaobin
    2014, 65(12):  4726-4733.  doi:10.3969/j.issn.0438-1157.2014.12.011
    Abstract ( 462 )   PDF (700KB) ( 328 )  
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    An experiment was performed to study the heat transfer characteristics of liquid flow through two multi-port extruded (MPE) micro-tubes with water, ethanol, acetone and ethanol/water mixtures. The cross-section geometries of two tubes were rectangular (approximate square) and circular, and with hydraulic diameters of 0.72 and 0.86 mm respectively. The results showed that at Reynolds number (Re) below 500, Nusselt number (Nu) decreased with increasing heat flux but Nu approached a minimum for increasing heat flux at Re > 500. Experimental results showed that such change was caused by the effect of entrance function and conjugate heat transfer. The experimental Nu of the circular multi-tube was higher than that of rectangular multi-tube. For ethanol, pressure drop decreased dramatically with increasing thermal resistance beginning at a low thermal resistance. Additionally, the higher the inlet temperature, the smaller the slope of pressure drop decrease against thermal resistanc. Further investigations of water, ethanol and acetone were conducted. Nu of ethanol were highest and those of water were the lowest among three solutions with the same heat flux and inlet temperature. Experiments of rectangular multi-tube, with different mixing ratios of ethanol/water showed that the trend of Nu against Re remained unchanged at low ethanol concentration. Furthermore, the higher the ethanol concentration, the faster the growth rate of Nu against Re and the greater the Nu difference between adjacent concentrations. Theoretical reasons for this remains to be further studied.
    Entropy analysis of CO2-air microchannel evaporator in two-phase flow region
    LÜ Jing, SHI Dongdong, XU Feng, ZHU Siqian
    2014, 65(12):  4734-4741.  doi:10.3969/j.issn.0438-1157.2014.12.012
    Abstract ( 234 )   PDF (749KB) ( 190 )  
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    Microchannels have become a hot issue in heat exchanger research. In this paper, the microchannel evaporator with CO2 was taken as research subject. A new entropy mathematical model was proposed for microchannel evaporator with CO2 flowing inside and air flowing outside. Phase transition existed on both sides. Entropy generation number Ns represented the losses due to temperature difference of heat transfer and pressure drop. A steady state distributed parameter model for the microchannel evaporator was established to solve entropy generation number. Comparisons of analytical and existing experimental data were made to verify and validate the model. The effects of mass flow rate of CO2 and air, CO2 evaporation temperature and inlet air temperature on system entropy generation number were analyzed. The results from the mathematic model showed that mass flow rate of CO2 had little effect on system entropy generation number. System entropy was mostly caused by temperature difference of heat transfer between CO2 and air sides. With rising inlet air temperature, entropy generation number became larger. While with rising CO2 evaporation temperature, system entropy generation number decreased. With increasing air mass flow rate, system entropy generation number increased. The higher the evaporation temperature, the greater the impact of air mass flow rate on system entropy generation number.
    Correlation analysis between Songhua River water quality and fouling resistance in heat exchanger tube
    XU Zhiming, ZHANG Yilong, LIU Zuodong, ZHANG Zhongbin
    2014, 65(12):  4742-4748.  doi:10.3969/j.issn.0438-1157.2014.12.013
    Abstract ( 337 )   PDF (968KB) ( 232 )  
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    The influence of the Songhua River water quality on the fouling resistance in heat transfer process was studied. The water quality variation in the heat transfer was measured in three types of heat exchange tube, including a general circular tube and two enhanced tubes, alternating elliptical axis tube and discrete double inclined ribs tube. The measured water quality parameters are pH, alkalinity, conductivity, DO, Ca2+ and Fe2+ concentrations. The fouling resistance is correlated with the water quality parameters with the gray correlation method. The results show that the parameter correlation order is the same for the two enhanced tubes. The variation tendency of fouling resistance is the same as two of the water quality parameters and opposite of the other parameters. Compared with circular heat exchange tube, the enhanced heat exchange tube affects not only the water quality parameters, but also the parameter correlation.
    Direct contact condensation of steam bubbles with non-condensable gas
    QU Xiaohang, TIAN Maocheng, ZHANG Guanmin, LUO Lincong
    2014, 65(12):  4749-4754.  doi:10.3969/j.issn.0438-1157.2014.12.014
    Abstract ( 335 )   PDF (644KB) ( 319 )  
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    The condensation behavior and heat transfer characteristics of steam bubbles with air were investigated by visual experiments, with steam mass fraction between 0.5 and 0.8. Bubbles of gas mixture were injected into cool water at two different temperatures through nozzles of diameter 1.5 and 3 mm. The condensing processes of bubbles were recorded by high speed camera and the thermodynamic parameters of bubbles were obtained by the variation of bubble volumes, from which the condensing heat transfer coefficients were calculated. The results show that the bubble deforms continuously when it condenses and a hollow forms in the middle of the bubble at the beginning of the condensing process. The condensing heat transfer coefficient decreases as cool water temperature decreases and bubble volume increases, while it is not affected by the nozzle diameter. The condensing heat transfer is deteriorated by the noncondensing gas. A correlation to predict the heat transfer coefficients is established using all the 65 data obtained in this experiment.
    PIV experiment for tube fitted with rotors
    HE Lichen, GUAN Changfeng, ZHANG Chongwen, HE Changjiang, HE Jianyun, YAN Hua
    2014, 65(12):  4755-4759.  doi:10.3969/j.issn.0438-1157.2014.12.015
    Abstract ( 472 )   PDF (1180KB) ( 351 )  
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    Particle image velocimetry was used to study the tubes fitted with and without "Jienengxin" rotors and the plain tube, and the velocity fields and turbulent kinetic energy distribution were obtained. The experimental results reveal that, compared with the plain tube, the flow field of tube is changed with the rotors inserted in. The axial velocity distribution turns to M type from parabolic type; the radial velocity is an order of magnitude higher than that of plain tube in a large part of the axial region, with positive and negative values alternatively, namely the direction of velocity changes constantly. The turbulent kinetic energy is promoted remarkably, which means that better heat transfer effect could be achieved by "Jienengxin" rotors.
    Effect of liquid flow behaviour on performance of corrugated structured packing
    LI Hong, YAO Yuebin, WANG Fangzhou, GAO Xin, LI Xingang
    2014, 65(12):  4760-4766.  doi:10.3969/j.issn.0438-1157.2014.12.016
    Abstract ( 306 )   PDF (888KB) ( 219 )  
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    Five corrugated structured packings are selected based on different liquid flow patterns including seepage flow and film flow. The hydrodynamic and mass transfer performance are studied in order to explore the effect of liquid flow patterns on the performance of structured packings. The experimental results show that liquid mainly presents a seepage flow in the porous structure of SCFP type packing, which benefits the lateral spreading of liquid and uniform distribution of liquid membrane. The SCFP type packing shows the highest mass transfer efficiency and lowest pressure drop when the F factor is lower. Liquid displays a partly seepage flow in the special structure of DMⅢ type packing, which can promote the liquid exchange between two sides of one sheet and intensify liquid turbulence, increasing mass transfer efficiency and reducing pressure drop compared with DMⅠand DMⅡtype structured packings. Liquid flows in the form of film on the surface of BX and DMⅠtype packings and this flow pattern results in a high velocity and a short residence time of liquid film. Thus the mass transfer efficiency of BX and DMⅠtype packings is lower than that of SCFP and DMⅢ type packings. This study shows that the structured corrugated packing with seepage flow presents good performance, opening up a new method to develop structured corrugated packings.
    Numerical simulation of flow pattern transition for gas-liquid two-phase flow in helical square ducts
    ZHOU Yunlong, ZHANG Liyan
    2014, 65(12):  4767-4774.  doi:10.3969/j.issn.0438-1157.2014.12.017
    Abstract ( 462 )   PDF (3545KB) ( 630 )  
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    A numerical analysis of air-water two-phase flow characteristics in helical square ducts was made using the CLSVOF (coupled level set and volume of fluid) multiphase model. The range of gas superficial velocity was 0.1—2.5 m·s-1, and liquid superficial velocity was 0.09—4.5 m·s-1. An investigation of effects of curvature diameter and helix angle on flow pattern transition was made. The air-liquid two-phase flow pattern map was drafted under different flow conditions. Compared with the traditional interface tracking method, the CLSVOF method could get a more accurate gas-liquid interface. With helix angle increasing, the conversion boundary from plug flow to bubbly flow moved towards decreasing UL, but only slightly. The conversion boundary from plug flow to slug flow moved towards decreasing UL. With coil diameter increasing, the conversion boundary from plug flow to bubbly flow moved towards decreasing UL. The conversion boundary from plug flow to slug flow moved towards decreasing UL and increasing UG. Flow pattern transition was different from Murai flow pattern.
    Experimental study and numerical simulation on jet streaming in deep bubbling fluidized-bed
    YAN Shuren, LIANG Yongshi, ZHANG Yongmin
    2014, 65(12):  4775-4784.  doi:10.3969/j.issn.0438-1157.2014.12.018
    Abstract ( 235 )   PDF (4456KB) ( 200 )  
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    By means of optical fiber probe, the jet streaming phenomenon in FCC baffle-free strippers was studied in a large cold-model experimental unit. Its properties as well as its development with bed height were studied. A newly developed computational particle fluid dynamics (CPFD) model was further used to explore this phenomenon. Jet streaming mainly happened near the stripper wall, resulting in serious non-uniformity in circumferential solids distribution. The strength of jet streaming decreased with increasing bed height. CPFD model could successfully predict the existence of jet streaming in this system. Although the predicted jet streaming strengths at higher bed heights were slightly overestimated, its trend with increasing bed height qualitatively agreed with the experimental fact. The deeper understanding acquired in this study can be used as a good reference for design and troubleshooting of the industrial FCC strippers.
    Effect of hydration CaO on production of bio-oil by catalytic pyrolysis of Nannochloropsis sp.
    YANG Lin, ZHANG Xiuli, GUO Qingjie
    2014, 65(12):  4785-4792.  doi:10.3969/j.issn.0438-1157.2014.12.019
    Abstract ( 355 )   PDF (791KB) ( 370 )  
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    The catalytic pyrolysis of Nannochloropsis sp. was carried out in a bench-scale fixed bed reactor using hydration CaO catalyst. The effect of the hydration CaO dosage on pyrolysis product yield and bio-oil compositions was investigated. The regeneration characteristics of used CaO by mean of direct and intensified regeneration methods was also examined. The results showed that bio-oil quality improved significantly with increase of dosage. The bio-oil yield over the hydration CaO (mass ratio of catalyst to Nannochloropsis sp. was 1:3) was 28.5%, and it had low oxygen content, high calorific value, low kinetic viscosity, and low moisture content. Compared with direct pyrolysis oil, for the catalysis pyrolysis oil there were low contents of carboxylic compounds and hydroxyl compounds, and high content of aliphatic and aromatic hydrocarbons. The results from the regeneration experiments indicated that the catalytic activity was still higher for direct regeneration, and if water-washing intensified step was employed, leading to the significant improvement of bio-oil quality due to increase of the surface and calcium content.
    Pyrolysis characteristics of cellulose from ionic liquid regeneration
    WANG Peng, GONG Xun, ZHANG Biao, LENG Erwei, CHEN Zhenguo, XU Minghou
    2014, 65(12):  4793-4798.  doi:10.3969/j.issn.0438-1157.2014.12.020
    Abstract ( 248 )   PDF (1038KB) ( 305 )  
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    Microcrystalline cellulose PH-101 was dissolved by the ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl). Two kinds of regenerated cellulose with lower crystallinity (C1 and C2) were obtained by different regeneration methods. XRD was used to determine crystallinity of materials, thermogravimetric (TG) was used to determine thermal stability, and scanning electron microscopy (SEM) was used to observe the difference of morphology. The effect of crystallinity on pyrolysis characteristics of cellulose was obtained by analyzing the pyrolysis products from the cellulose with different degrees of crystallinity. Py-GC/MS results showed that the cellulose with lower degree of crystallinity had lower levoglucosan yield but higher yield of small molecule components.
    Preparation and catalytic performance of magnetic mesoporous silica supported basic ionic liquids
    ZHANG Yaping, JIAO Qingze, WU Qin, LI Hansheng
    2014, 65(12):  4799-4804.  doi:10.3969/j.issn.0438-1157.2014.12.021
    Abstract ( 357 )   PDF (549KB) ( 292 )  
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    Magnetic mesoporous silica was modified with 3-mercaptopropyl trimethoxysilane, and then ionic liquid with different alkyl chains was immobilized on magnetic mesoporous silica via free radical addition reaction between sulfydryl group and double bond. The catalysts were characterized with FTIR, XRD, elemental analysis and vibrating sample magnetometer. Finally, the catalytic activity of the catalyst was evaluated through catalytic transesterification reaction of glycerol trioleate with methanol. Ionic liquid loading, specific surface area and pore volume of the catalyst decreased with the increase of alkyl chain of ionic liquid. When the alkyl chain of ionic liquid was octyl group, dodecyl group or hexadecyl group, the yield of methyl oleate was higher than 95%, and after three cycles, the yield of methyl oleate was still higher than 90%.
    Microwave-assisted preparation of g-Fe2O3 as SCR catalysts
    WANG Dong, ZHANG Xinli, LU Chunmei, HAN Kuihua, PENG Jiansheng, XU Liting
    2014, 65(12):  4805-4813.  doi:10.3969/j.issn.0438-1157.2014.12.022
    Abstract ( 232 )   PDF (782KB) ( 200 )  
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    γ-Fe2O3 and a-Fe2O3 catalysts were prepared respectively via a novel microwave pyrolysis method using FeSO4·7H2O and Fe(NO3)3·9H2O as ferrous source. Crystalline phase and microstructure of catalysts were characterized by X-ray diffraction(XRD), mercury intrusion porosimetry(MIP), N2 adsorption-desorption and NH3-SCR activity of different catalysts were investigated. SCR reaction rates over the catalysts at different temperatures were obtained by unitary processing, and SCR activities over γ-Fe2O3 and vanadium-based catalysts were compared. The effects of O2 concentration, molar ratio of NH3/NO, SO2, and H2O on SCR activity of γ-Fe2O3 catalyst were also studied. Pure γ-Fe2O3 catalyst could be obtained via this novel microwave pyrolysis method, and showed higher crystallinity than a-Fe2O3 catalyst. γ-Fe2O3 catalyst had broader pore size distribution as well as appropriate ratios of mesopores and macropores. Meanwhile, γ-Fe2O3 catalyst exhibited better SCR activity than a-Fe2O3 catalyst. The highest NOx conversion of γ-Fe2O3 catalyst was up to 96% at 400℃ and SCR reaction rates normalized by surface area were three times higher than that of a-Fe2O3 catalyst at 300, 325 and 350℃, respectively. The optimum molar ratio of NH3/NO and O2 concentration for selective catalytic reduction over γ-Fe2O3 catalyst were recommended to be 1 and 3.5% (vol), respectively.
    Molecular dynamics simulation of water molecules adsorbed at muscovite (001) surface
    XU Yao, LIU Yuelong, LIU Gousheng
    2014, 65(12):  4814-4822.  doi:10.3969/j.issn.0438-1157.2014.12.023
    Abstract ( 263 )   PDF (12982KB) ( 1172 )  
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    As an important separation technique, microscopic phenomena of solid/liquid interface are crucial in flotation process. A molecular dynamics simulation is performed with PCFF_phyllosilicates force field to study the adsorption of water molecules on the muscovite surface, and atomic density profiles, hydrogen bond profiles, radical distribution function, mean squared displacement and density field are calculated. Results show that at a surface with water coverage larger than 1, the number of water molecules in the first three layers near the muscovite (001) surface will be stable with the increase of water molecules; water molecules closed to the surface represent much more ordering than those far from the surface; "solid effect" in the microscopic phenomena in the water solution is stressed by change trends of atomic density profiles and hydrogen bond profiles. It is found that K+ have poor mobility, especially in the z direction, and the stability of [Si4Al2]-K+ structure is proven via the density field of K+.
    Lactic acid recovery from fermentation by bipolar membrane electrodialysis and ionic migration
    LIN Han, WANG Qunhui, WANG Lijuan, LI Yan, CHEN Huanxi
    2014, 65(12):  4823-4830.  doi:10.3969/j.issn.0438-1157.2014.12.024
    Abstract ( 269 )   PDF (1459KB) ( 318 )  
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    A series of factors were examined in the separation of lactic acid (HLa) from lees fermentation by bipolar membrane electrodialysis. When the fermentation with the initial HLa concentration of 13.5 g·L-1 was treated by bipolar membrane electrodialysis under the conditions of voltage 27 V, feeding concentration ratio 1.3, and flow rate 20 L·h-1 for 10 h, HLa concentration of discharging tank was 20.95 g·L-1, which was 1.6 times the initial concentration, a significant concentrated effect. Moreover, the analysis of acid ion migration shows that immigration rate of lactic acid ions is significantly higher than that of other acid ions. The relative separation efficiency of HLa to propionate and acetic acid are lower.
    Advanced energy saving in vitamin evaporation crystallization section at low temperature with self-heat recuperation technology
    WU Yifei, HAN Dong, HE Weifeng, ZHEN Pujie, PU Wenhao, YUE Chen
    2014, 65(12):  4831-4838.  doi:10.3969/j.issn.0438-1157.2014.12.025
    Abstract ( 331 )   PDF (583KB) ( 252 )  
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    To solve the problem of high consumption and great emission of the evaporation unit in production of a vitamin, an advanced process is proposed based on the self-heat recuperation technology. The sensible and latent heat of the effluent stream is recuperated and reused to heat the inlet stream of flash evaporator by vapor recompression without any heat addition. The advanced process is evaluated by energy and exergy analysis. The relation between energy consumption and the minimum heat transfer temperature difference are studied, as well as the effect of adiabatic efficiency on energy required. The results indicate that the advanced system with self-heat recuperation technology is able to save great energy and exergy. The energy input is decreased by 73.0% and the exergy input is decreased by 68.3%. There is a larger potential space for latent heat than sensible heat, which only accounts for 6.5% of the total heat recycled. Although larger minimum temperature difference needs less heat transfer area, it requires more energy input. Higher adiabatic efficiency and lower superheat mean less energy required.
    Start-up process of crack gas compressors via dynamic simulation
    SONG Guang, ZHAO Yongchen, ZHANG Shengfu, QIU Tong, ZHAO Jinsong
    2014, 65(12):  4839-4843.  doi:10.3969/j.issn.0438-1157.2014.12.026
    Abstract ( 241 )   PDF (800KB) ( 511 )  
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    The crack gas compressors are the core equipment of the ethylene plant, whose smooth start plays an important role in the whole plant's start-up process. In traditional start-up process, the crack gas compressors start with the crack gas, which is replaced by other working mediums in recent years, such as nitrogen, natural gas or mixed hydrocarbon. Due to the impossibility to test on the equipment, the chemical engineering simulation technology has become the important tool to solve these problems. In this paper, according to the "steady-state/dynamic/start-up" method, a steady-state simulation model of crack gas compressors is built, and the steady-state operation parameters of the crack gas, nitrogen and mixed hydrocarbon were determined. Then, the steady-state model was converted to the dynamic model. At last, the safety and feasibility of transformation process between various working conditions were verified.
    Cold energy combination of LNG light hydrocarbon separation and ethylene plant
    ZHANG Xiaofeng, FENG Xiao
    2014, 65(12):  4844-4849.  doi:10.3969/j.issn.0438-1157.2014.12.027
    Abstract ( 234 )   PDF (400KB) ( 190 )  
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    Different level of cold energy is needed in the cryogenic separation process of an ethylene plant, so the ethylene separation process can be treated as a cold sink. Heat is needed in a LNG gasification process which can be treated as a cold source. This work combines the ethylene cryogenic separation process with the LNG gasification process, so that the cold utility demand in the ethylene cryogenic separation and the heat utility demand in the LNG gasification process are both reduced. The light hydrocarbons which get from LNG separation process can be a perfect cracking feed for the ethylene plant. A plant with a 3000000 t·a-1 LNG process and a 640000 t·a-1 ethylene process is used as a case study. The simulation results show that LNG plant can provide 41464 kW cold utility for the ethylene plant, reducing 75% refrigerant consumption of the ethylene plant. It also provides 650000 t·a-1 high quality cracking feed for the ethylene plant.
    Modeling, simulation and analysis for co-feed process of coal and coke-oven gas to olefins
    MAN Yi, YANG Siyu, XIANG Dong, QIAN Yu
    2014, 65(12):  4850-4856.  doi:10.3969/j.issn.0438-1157.2014.12.028
    Abstract ( 249 )   PDF (509KB) ( 249 )  
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    Olefins are one of the most important platform chemicals. Developing coal-to-olefins (CTO) processes is regarded as one of promising alternatives to oil-to-olefins process. However, CTO suffers from high CO2 emission due to the high carbon contents of coal. In China, there is 7×1010 m3 coke-oven gas (COG) produced in coke plants annually. However, most of the hydrogen-rich COG is utilized as fuel or discharged directly into the air. Such situation is a waste of precious hydrogen resource and serious economic loss, which causes serious environmental pollution either. This paper proposes a novel co-feed process of coal and COG to olefins in which CH4 of COG reacts with CO2 in a dry methane reforming unit to reduce emissions, while the steam methane reforming unit produces H2-rich syngas. H2 of COG can adjust the H/C ratio of syngas. The analysis shows that the energy efficiency of the co-feed process increases about 10 %, while at the same time, CO2 emission is reduced by around 95 % in comparison to the conventional CTO process.
    AEA combined with differential evolution and its application on parameter estimation
    HE Pengfei, LI Shaojun
    2014, 65(12):  4857-4865.  doi:10.3969/j.issn.0438-1157.2014.12.029
    Abstract ( 197 )   PDF (523KB) ( 195 )  
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    Focusing on the demerits of AEA (Alopex-based evolutionary algorithm), this paper proposed a modified AEA algorithm (MAEA), which was fused AEA with differential evolution (DE). In order to enhance the performance of the algorithm, the generation method of population in AEA was improved by applying an improved DE operation to AEA. The modified algorithm not only takes advantage of heuristic search and deterministic search of AEA, but also increases the population diversity and is adapted to global search and local search. Then the MAEA algorithm was tested by 21 benchmark functions,the results show that MAEA outperforms DE, MDE and AEA. Further comparison results between MAEA algorithm and a representative state-of-the-art algorithm(ISDEMS) indicate that, the performance of the modified algorithm is significantly improved, in both accuracy and stability. Furthermore, the algorithm was applied to the parameter estimation of the models of fermentation dynamics, and the satisfactory results were obtained.
    Fault detection and diagnosis for nonlinear and multimode processes using Bayesian inference based PKPCAM approach
    LU Chunhong, XIONG Weili, GU Xiaofeng
    2014, 65(12):  4866-4874.  doi:10.3969/j.issn.0438-1157.2014.12.030
    Abstract ( 224 )   PDF (605KB) ( 249 )  
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    A probabilistic kernel principal component analysis mixture model (PKPCAM) based on Bayesian inference was proposed to detect and diagnose the fault in the nonlinear and multimode processes. In PKPCAM, each operating mode was characterized by a local probabilistic kernel principal component, leading to a series of components corresponding to multiple operation conditions. Firstly, process data were projected from the original measurement space into the high-dimensional feature space. Then the probabilistic kernel principal component analysis mixture model was estimated in the feature space and used to characterize the multiple local components from the viewpoint of probability. Finally, utilizing the posterior probability of the monitored sample in kernel subspace, according to Mahalanobis distance within the local mode, the Bayesian reference based global probability index was proposed for fault detection. And meantime, using the relative contribution of variable within mode, global contribution index was derived to perform diagnosis. Comparing to the two methods based on the sub-principal component analysis using k-means clustering and the kernel principal component analysis, the feasibility and effectiveness by the proposed Bayesian inference based PKPCAM method for fault detection and diagnosis in nonlinear and multimode process was validated on Tennessee Eastman process.
    Recursive PLS modeling based on model performance assessment and its application
    XU Ouguan, CHEN Xianghua, FU Yongfeng, LI Lijuan
    2014, 65(12):  4875-4882.  doi:10.3969/j.issn.0438-1157.2014.12.031
    Abstract ( 332 )   PDF (652KB) ( 443 )  
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    In order to reduce the model updating frequency of recursive partial least squares (RPLS) modeling methods, a RPLS model based on the model performance assessment (MPA-RPLS) is developed. Firstly, a confidence limit of the model is generated automatically based on the initial behavior of a process. And a root mean squared error of prediction (RMSEP) is used as a performance index to evaluate the model. Base on the results of the model performance assessment, the model updating is selectively activated, in the meanwhile, the confidence limit is also updated. Subsequently, a moving average filter is integrated into the model to eliminate the noise embbeded in variables, and the effect of the noise on the model performance is then investigated. At last, the developed model is applied to a chemical reaction process, hydro-isomerization process of C8-aromatics. Simulation is run based on a large number of industrial data. The simulation results show that the computational efficiency is improved greatly (model updating frequency is reduced greatly) by the developed model, while a minor loss of the prediction accuracy is found. The noise embedded in variables could be dealt with effectively by the moving average filter, hence the prediction accuracy is improved.
    Soft-sensor modeling for ethylene distillation product quality based on vector projection metabolism support vector machine
    ZHENG Boyuan, SU Chengli, LI Ping, SU Shengjiao
    2014, 65(12):  4883-4889.  doi:10.3969/j.issn.0438-1157.2014.12.032
    Abstract ( 324 )   PDF (693KB) ( 214 )  
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    A metabolism support vector machine (SVM) based modeling method was proposed to solve the problems that slowed down computing speed and caused poor stability during SVM incremental learning. Firstly, vector projection algorithm was used to pre-extract training samples, in order to reduce the number of samples and improve SVM modeling speed. Secondly, a new sample "metabolism"principle was pulled into the SVM incremental learning process, for addressing "explosion" of training samples number which was caused by adding new samples continuously. Finally, the vector projection metabolism SVM was utilized in ethylene distillation product quality soft-sensor modeling. The experiment results showed that vector projection metabolism SVM had better prediction result than SVM and LSSVM.
    Adaptive optimization for gold cyanidation leaching process
    ZHANG Jun, MAO Zhizhong, JIA Runda, HE Dakuo
    2014, 65(12):  4890-4897.  doi:10.3969/j.issn.0438-1157.2014.12.033
    Abstract ( 247 )   PDF (1072KB) ( 194 )  
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    The adaptive real-time optimization (RTO) of gold cyanidation leaching process in a hydrometallurgy plant was investigated. To solve plant-model mismatch, an adaptive real-time optimization strategy based on the modifier adaptation method was proposed, and the real plant data and gradient information were used to correct the original optimization problem iteratively to drive its solution to converge to the optimal set point for the plant. The simulation results showed that in the presence of moderate measurement noise and model uncertainty, the iterates based on the proposed adaptive strategy could converge to the optimal set point for the plant after several iterations and moreover the step of parameter estimation was not necessary, laying an important foundation for the successful implementation of the plant-wide optimization and control for hydrometallurgy process.
    Adaptive soft sensor method and application in determination of dynamic fluid levels
    WANG Tong, GAO Xianwen, LIU Wenfang
    2014, 65(12):  4898-4904.  doi:10.3969/j.issn.0438-1157.2014.12.034
    Abstract ( 277 )   PDF (728KB) ( 231 )  
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    For the measurement of dynamic liquid level of oil wells, the traditional manual work has many shortcomings, such as low precision, poor real-time performance etc. According to analysis of actual production data, a soft sensor method based on empirical mode decomposition (EMD) and black hole-least squares support vector machine (BH-LSSVM) was proposed to realize soft sensor modeling of dynamic liquid level. In oilfield production, static model cannot fully reflect the production conditions which may lead to model failure. Therefore a dynamic model was proposed by building a performance evaluation module, which could improve adaptive ability and prediction precision. The proposed method had higher measurement accuracy of dynamic liquid level and stronger adaptive ability for production fluctuation, which met requirement of oil production. Automation in oil production was improved.
    Multiple dynamic kernel clustering based online monitoring for batch processes
    WANG Yajun, SUN Fuming
    2014, 65(12):  4905-4913.  doi:10.3969/j.issn.0438-1157.2014.12.035
    Abstract ( 245 )   PDF (776KB) ( 178 )  
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    Since weak faults induced by large fluctuations under poor initial conditions could not be effectively detected by traditional multivariate statistical monitoring methods, a novel kernel principal component analysis monitoring strategy based on multiple dynamic kernel clustering (DKCPCA) was proposed to improve weak faults detection performance for multi-stage batch processes. The proposed method firstly combined auto-regressive moving average exogenous time series model and kernel principal component analysis (KPCA). The dynamic kernel PCA model was built for each batch in each stage. Then hierarchical clustering was implemented through load matrix similarity among batch models. Finally, the batch data belonging to the same cluster were unfolded to build dynamic kernel PCA model again. The multiple models were established along with different cluster numbers. When online monitoring, multiple model selection strategy was given to improve monitoring precision. The monitoring method was applied to fault detection for benchmark of fed-batch penicillin production. The monitoring results showed that the proposed method had better performance than DKPCA and MKPCA.
    Optimization of inter-plant hydrogen system with purification reuse in petrochemical complex
    DENG Chun, ZHOU Yeyang, CHEN Jie, FENG Xiao
    2014, 65(12):  4914-4920.  doi:10.3969/j.issn.0438-1157.2014.12.036
    Abstract ( 193 )   PDF (547KB) ( 170 )  
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    Hydrogen-rich gas from fertilizer plants and ethylene plants can be sent to refinery in a petrochemical complex. It can alleviate the deficit of hydrogen in refinery. Thus the optimization of inter-plant hydrogen network in petrochemical complex is important. A superstructure of inter-plant hydrogen network with purification reuse is constructed. The corresponding mathematical model with the total annualized cost as objective function is proposed and the commercial optimization software GAMS is utilized to solve the problem with DICOPT as a solver. The hydrogen network of a petrochemical park is optimized. The results shows that the total annual cost can be reduced by 33.1% comparing to the current hydrogen network.
    Modeling of ethylene cracking furnace yields based on transfer learning
    ZHOU Shuheng, DU Wenli
    2014, 65(12):  4921-4928.  doi:10.3969/j.issn.0438-1157.2014.12.037
    Abstract ( 240 )   PDF (611KB) ( 512 )  
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    Ethylene cracker generally utilizes petroleum products as raw materials, and turn the long-chain hydrocarbon molecules into a variety of short chain hydrocarbons like gaseous hydrocarbons and a small amount of liquid hydrocarbons at high temperature, thereby obtaining ethylene, propylene and other products. Establishing the yield model for main products is of great significance to advanced control, operation optimization of the pyrolysis furnace in theory and practice. Due to the semi-continuous and periodic characteristics of cracking furnace, establishing a yield model for each condition is time-consuming. Considering the temperature, residence time and pressure have common effect on product yields, so this article uses these similarities exist in the new and old processes, supplemented with transfer learning to accomplish quick modeling for different conditions. Compared to previous studies, this method can be able to fully exploit the information contained in the historical data from a small amount of new data. Meanwhile, building a model of ethylene in the process of cracking furnace, case studies demonstrate the efficacy of the developed methodology.
    Atmospheric tower energy optimization based on EGO
    YE Zhencheng, QIAN Zhiyuan, LUO Na
    2014, 65(12):  4929-4934.  doi:10.3969/j.issn.0438-1157.2014.12.038
    Abstract ( 180 )   PDF (541KB) ( 206 )  
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    Energy consumption of crude oil distillation unit accounts for about 25% to 30% of refinery total energy. Satisfying the request of product yield and quality, optimizing crude distillation column operating conditions can effectively reduce energy consumption. Using stochastic optimization algorithms directly optimizing model of atmospheric tower is time-consuming and low efficient. In this paper, efficient global optimization algorithm based on surrogate model is applied to optimization of atmospheric tower's heat recovery. Kriging surrogate model is used as a replacement to the original model which is time-consuming in iterative optimization process. The result shows that this method decreases 90% number of assessment and decreases 85% optimization time compared with particle swarm optimization and realizes energy savings and meets product separation accuracy requirements.
    Multi-stage fusion modeling for penicillin fermentation process based on EM algorithm
    XIONG Weili, YAO Le, XU Baoguo
    2014, 65(12):  4935-4941.  doi:10.3969/j.issn.0438-1157.2014.12.039
    Abstract ( 254 )   PDF (670KB) ( 233 )  
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    Penicillin fermentation process has the feature of the distinct phases, which can be seen from some key operating variables. In this paper, the key process variable, namely, the cold water flow rate was taken as the scheduling variable, which was then classified by the fuzzy C-means clustering algorithm. The cluster centers were considered as the main operating points of the penicillin fermentation process. Local models were constructed around each operating point based on EM algorithm. Thereafter, sub-models were combined togethter according to the posterior distribution of the scheduling variable. The feasiblity and effectiveness of the proposed method was illustrated through the Pensim simulation platform.
    Interfacial turbulence in desorbing surface of tension-lowering solutes from water
    JIN Wu, ZENG Aiwu, YANG Ning, ZHAO Song
    2014, 65(12):  4942-4947.  doi:10.3969/j.issn.0438-1157.2014.12.040
    Abstract ( 211 )   PDF (2521KB) ( 247 )  
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    The schlieren system was used to capture the onset of transition to turbulence and the interfacial turbulence in desorbing surface of tension-lowering solutes from aqueous solution. Convective structure in ethanol-water solution, isopropanol-water solution and acetone-water solution was alike. When the mass transfer process started, a rapidly growing turbulent region was observed on the surface. Several small round cells appeared on the edge of the expanding turbulent region. These small cells gradually developed into polygon structures as reported by many investigators. After the short instability process, the structures changed into ring-like shapes. In ethyl acetate-water solution, the structures remained clustered shape, and turbulence intensity was stronger. Structural features and turbulence intensity of interfacial convection depended on experimental operating conditions and physical properties of the system.
    Influence of agro-biomass addition on Changping coal ash melting characteristics
    TANG Jianye, CHEN Xueli, QIAO Zhi, LIU Aibin, WANG Fuchen
    2014, 65(12):  4948-4957.  doi:10.3969/j.issn.0438-1157.2014.12.041
    Abstract ( 325 )   PDF (14412KB) ( 255 )  
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    The effects of rice straw (DC) and cotton stalk (MG) addition on Changping (CP) coal ash melting characteristics were studied with high-temperature optical microscopy, scanning electron microscopy coupled with energy dispersive spectrometer (SEM-EDS), standard ash fusion temperature (AFT) tests and X-ray diffraction (XRD) analyses. The AFT of CP coal could be reduced effectively by adding both agricultural residues. In weak reducing atmosphere at high temperature, refractory mullite and quartz were main minerals of CP coal ash. The presence of agricultural residues could form low melting eutectic minerals, such as leucite, ringwoodite and anorthite, decreasing the AFT of CP coal. High temperature images of ash particles showed that CP coal ash fusion behavior was prolonged softening and subsequent melting of solid phases that resulted in sluggish flow and depressed dissolution of the refractory constituents. However, during the melting process of DC blended CP coal ash, active melts with low viscosity that could promote the reaction between the minerals and quickly dissolve the residual refractory were formed.
    Experimental characteristics of solar organic Rankine cycle system
    SONG Jianzhong, ZHANG Xiaosong, LI Shuhong, YAO Qikuang, GU Weiwei
    2014, 65(12):  4958-4964.  doi:10.3969/j.issn.0438-1157.2014.12.042
    Abstract ( 245 )   PDF (1143KB) ( 546 )  
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    To study the performance of solar organic Rankine cycle (ORC) system, a low temperature solar ORC system is proposed and constructed. The system employs R245fa as the working fluid in the power cycle and WD350 heat transfer oil as the heat transfer fluid in the solar collector. The experimental installation consists of a trough solar collector, a screw expander, a working fluid pump, a heat regenerator, a water cooled condenser, and a vapour generator. When the solar beam radiation is about 400 W·m-2 in the experiment, the thermal oil temperature at the outlet of solar heat collector can reach up to 140℃. The collecting efficiency of the collector is 60% at the outlet oil temperature of 110℃. When the working mode of system changes from basic ORC to regenerative cycle, the calculated efficiency of the system is improved from 9.3% to 10.8%, and the experimental value is improved from 1.57% to 1.67%. The measured exergy efficiency of the system is about 10%. The value under regenerative cycle mode is higher than that under the basic ORC mode. The cycle performance at different working fluid flow rates was also studied. The measured maximum average power output was obtained at 386.27 W and working fluid flow rate of 6.88 kg·min-1. With the increase of working fluid flow rate, both expander inlet pressure and work output increase at fixed heat source temperature. With the increase of heat source temperature, the expander inlet temperature and pressure, and the power output increase at fixed flow rate.
    Double-salt precipitation of Ca(NO2)2 derived from multi-pollution control process by ozone
    LIU Yingzu, ZHU Yanqun, MA Qiang, XU Chaoqun, WANG Zhihua, ZHOU Junhu, CEN Kefa
    2014, 65(12):  4965-4970.  doi:10.3969/j.issn.0438-1157.2014.12.043
    Abstract ( 309 )   PDF (619KB) ( 236 )  
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    Based on the double-salt precipitation method, an experimental study on the precipitation of calcium nitrite derived from wastewater treatment by oxidation of NOx and SO2 with ozone was performed. The effects of reaction temperature, reactant concentration, turbulence intensity on calcium nitrite precipitation efficiency were investigated by the variable-controlled method. Reaction temperature strongly influenced precipitation efficiency and optimal temperature was 80℃. Both increasing reactant concentration and turbulence intensity in the reaction process could enhance precipitation efficiency. Because double-salt precipitation was accompanied by separation of calcium hydroxide, precipitation efficiency could be improved by altering the separation conditions of calcium hydroxide.
    Enriched-air gasification of refuse derived fuel in bubbling fluidized bed
    NIU Miaomiao, HUANG Yaji, JIN Baosheng, WANG Yanyan, DONG Xinxin
    2014, 65(12):  4971-4977.  doi:10.3969/j.issn.0438-1157.2014.12.044
    Abstract ( 312 )   PDF (738KB) ( 349 )  
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    Enriched air gasification of two different refuse derived fuels (RDF) was performed in a bubbling fluidized bed reactor. Thermo-gravimetric analysis of the two RDFs was performed and the effect of temperature, equivalence ratio (ER) and oxygen percentage of enriched air was investigated. Both RDFs were composed of cellulose and plastics based materials. With increasing temperature from 650℃ to 800℃, concentrations of H2, CO and CH4 increased in both RDFs gasification. Gas yield and gasification efficiency were also improved. The combustible components first increased slightly and then decreased with increasing ER, while gas yield kept constant growth. The optimum ER values for RDF1 and RDF2 were 0.22 and 0.27 respectively for obtaining the highest gasification efficiency. The use of enriched air could improve gasification effectively and lead to higher heating value of the syngas. When oxygen percentage of enriched air was 45%, the maximum low heating values of the syngas for RDF1 and RDF2 were 8.6 MJ·m-3 and 9.2 MJ·m-3 respectively.
    Comprehensive evaluation index and performance analysis of organic Rankine cycle system considering environment impact
    ZHANG Xinming, YU Bingxian, WANG Chun
    2014, 65(12):  4978-4984.  doi:10.3969/j.issn.0438-1157.2014.12.045
    Abstract ( 361 )   PDF (552KB) ( 656 )  
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    In order to consider thermal economic performance and environmental impact of an organic Rankine cycle(ORC)system, the exergy parameter is used to quantify the environment influence of working fluids and composite performance indicator "comprehensive exergy efficiency integrated environmental influence" is proposed, which combines the environmental effect and cycle thermal economic performance. At thermal source of 150℃, the performance of working fluids of subcritical and transcritical ORC systems is evaluated by the composite performance indicator. Results show that R123 and R32 are suitable for subcritical and transcritical ORC systems respectively when considering the cycle thermal economic performance and refrigerant environmental impact. Although the net power output of transcritical ORC system is higher, the composite performance indicator shows that due to its high circulation evaporation pressure the leakage of working fluids increases. Therefore, subcritical ORC system is a better choice with considering the environmental protection and circulation performance.
    Shortcut nitrification and denitrifying phosphorus removal in improved A2/O technique with long SRT
    LUO Yahong, LI Dong, BAO Linlin, XU Da, CAI Yan'an, ZHANG Jie
    2014, 65(12):  4985-4996.  doi:10.3969/j.issn.0438-1157.2014.12.046
    Abstract ( 420 )   PDF (2272KB) ( 388 )  
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    Aiming at solving the contradiction of sludge retention time (SRT) between nitrification and dephosphorization, and enhancing the simultaneous nitrogen (N) and phosphorus (P) removal efficiency of the low C/N (P) ratio domestic sewage in the traditional A2/O process, an improved A2/O technique with long SRT was developed. The novel process could select and strengthen the activated sludge, and enrich the denitrifying phosphorus accumulating organisms (DPAO) with long SRT effectively. After washing out nitrite oxidizing bacteria (NOB), the reactor ran under the condition of SRT=19.6 d, and sludge concentration (MLSS)=5.5 g·L-1, hydraulic retention time (HRT)=8.2 h, sludge return ratio (R)=90%, nitrated liquid reflux ratio (r)=250%, dissolved oxygen (DO)=1.5—0.3 mg·L-1 for the A2/O zone. HRT=4 h, aeration cycle was 1 h, aeration time was 1 min (DO=0.3—0.5 mg·L-1) and settling time was 59 min for the intermittent aeration zone. Average removal rate of COD, NH4+-N, TP and TN reached 88.71%, 99.2%, 93.77% and 89.52% respectively, nitrosation rate (NO2--N/NOx--N) was up to 97.2%, and DPAO/PAO ratio in sludge was 95.5%, and the final effluent met the first class level A of the GB 18918—2002 standard. It was found that about 72.96% of COD in sewage was utilized by DPAO for PHA production to accumulate P, 15.75% of COD was consumed by heterotrophic denitrifying bacteria, and about 41.96% and 31.31% of N were wiped off through phosphorus removal and heterotrophic denitrifying. The discharged sludge was mainly composed of the biomass of DPAO and denitrifying bacteria, accounting for 82.74% and 17.24% respectively. The technique could reduce 58.76% of carbon source consumption and 44.6% of sludge discharge comparing to the traditional nitrogen phosphorus removal pathway.
    Enhanced magnetic cleaning in magnetic enhanced flocculation membrane filtration process
    WANG Jie, YANG Jun, JIA Hui, ZHANG Hongwei
    2014, 65(12):  4997-5003.  doi:10.3969/j.issn.0438-1157.2014.12.047
    Abstract ( 228 )   PDF (3525KB) ( 266 )  
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    On the basis of the characteristics of magnetic flocs and cake layer in the magnetic enhanced flocculation membrane filtration (MEFMF) process, processes of on-line and off-line magnetic enhanced cleaning (MEC) were designed. Magnetic cake layer was separated from fiber surface under the synergistic effect of magnetic field force and aeration shear force, in which way the goal of optimization of membrane cleaning was achieved. The magnetic enhanced cleaning process was added to magnetic enhanced flocculation membrane filtration for off-line cleaning of fouled membrane module in MEFMF process. In the magnetic cleaning process with device's magnetic induction 6 mT, aeration intensity 500 L·m-2·min-1, washing time to 5 min, backwash pressure 0.04 MPa, optimum cleaning effect could be achieved for flux recovery rate over 97%. In the enhanced cleaning process with magnetic field the magnetic seeding in the cake layer was magnetized, rendering the cake layer weak macro magnetism. Under the effect of the attached magnetic field the magnetized cake layer moved to the pole, therefore, membrane flux recovery rate was increased significantly. Furthermore, on-line intermittent magnetic cleaning could be more effective in removing colloidal and organic pollutants on membrane surface in the MEFMF process. The colloidal and organic pollutants were the major pollutants blocking membrane pores and causing irreversible fouling. As a result, membrane fouling was mitigated during the entire process.
    Thermal performance evaluation and prediction of enhanced vapor injection air source heat pump
    ZHANG Dong, LI Jinping, LIU Wei, NAN Junhu, WANG Linjun
    2014, 65(12):  5004-5009.  doi:10.3969/j.issn.0438-1157.2014.12.048
    Abstract ( 529 )   PDF (470KB) ( 280 )  
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    The enhanced vapor injection air source heat pump (EVI-ASHP) has better thermal performance at a low temperature, which has received much attention to supply hot water in cold region in recent years due to the growing space heating load and concern for environmental degradation. Environmental temperature is often below -5℃ in winter in cold region of China, and changes greatly throughout the year. Thus coefficient of performance (COP) under nominal working conditions (dry-bulb temperature of 7℃) is difficult to accurately reflect the actual energy-saving effect of the system. So, a set-up of EVI-ASHP system was built in Lanzhou, and thermal performance at different environmental temperatures and humidities was determined. COP of the EVI-ASHP system could reach above 6.5 when electromagnetic valve for vapor injection was off, and linear change of COP was observed. At a low temperature, when electromagnetic valve was on, COP was about 2.0. The fitting equations of the experimental data were obtained and verified, with average relative error below 3% compared with the experimental data from the set-up. An effective prediction method was established for thermal performance of the EVI-ASHP system at changeable environmental temperature and humidity, supplying a theoretical guidance for the application of the system in cold climate.
    Change of ultrastructure and composition of sugarcane bagasse in liquid hot water
    YU Qiang, ZHUANG Xinshu, YUAN Zhenhong, KONG Xiaoying, QI Wei, WANG Wen, WANG Qiong, TAN Xuesong
    2014, 65(12):  5010-5016.  doi:10.3969/j.issn.0438-1157.2014.12.049
    Abstract ( 366 )   PDF (3408KB) ( 320 )  
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    Native lignocellulosic biomass has limited accessibility to enzymes and microorganisms due to its complex cell wall structure of cellulose-hemicellulose-lignin. Therefore, pretreatment is a prerequisite to overcome recalcitrance of biomass and enhance bio-chemical conversion ratio of polysaccharides. Compared with other methods, high temperature liquid hot water pretreatment has the advantages of no chemical addition and less inhibitory products. In the present study, different structural changes at plant tissue, cellular, and cell wall levels were investigated to understand the decomposition mechanism of sugarcane bagasse cell wall in the liquid hot water pretreatment. Transmission electron microscopy (TEM) images showed that sugarcane bagasse cell walls were composed of middle lamella (ML) layers, primary wall (P) layers, and secondary wall layers (S). While after the pretreatment, the boundaries among the ML, P and S layers of treated samples could not be distinguished exactly. The data from scanning electron microscopy and energy dispersive X-ray analysis(SEM-EDXA)showed that migration of lignin happened among different cell wall layers. Moreover, pseudo-lignin, the degradation products of lignin and xylan, appeared on the surface of pretreated sugarcane bagasse. Furthermore, Raman spectra of treated sugarcane bagasse indicated that distribution of cellulose in the cell wall was homogenized, and the difference in chemical composition was reduced.
    Preparation of EPDM-g-MAZn ionomer by precipitation process and its influence on performance of PP/APP/PER IFR system
    WU Wei, HUI Linlin, WANG Zheng
    2014, 65(12):  5017-5022.  doi:10.3969/j.issn.0438-1157.2014.12.050
    Abstract ( 375 )   PDF (722KB) ( 300 )  
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    The EPDM (EPDM) zinc ionomer (EPDM-g-MAZn) grafted with maleic anhydride (MAH) was used as modifying agent in the PP/IFR system. The flame retardant mechanism of the EPDM-g-MAZn and its effects on the mechanical properties of PP/IFR were studied. Flame retardancy was good and tensile strength remained the same with the addition of EPDM-g-MAZn in PP/IFR. The impact strength of PP/EPDM-g-MAZn/IFR was 4.46 times higher than that of PP/IFR, but the tensile strength retention rate of PP/IFR was significantly higher than that of PP/EPDM-g-MAH/IFR. A crosslinked structure containing ZnO and EPDM segments was formed via the ionic bond of MAH. The interface bonding strength between PP and IFR was improved by the effects of the crosslinking agent as well as reinforcing agent. As a result, the mechanical properties of PP/IFR were effectively promoted.
    Effects of ultrasonic field on filling quality for micro-column arrays parts
    YU Tongmin, WU Yongqiang, HUANG Xiaochao
    2014, 65(12):  5023-5029.  doi:10.3969/j.issn.0438-1157.2014.12.051
    Abstract ( 409 )   PDF (827KB) ( 251 )  
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    The quality problem of plastics part caused by difficulty in melt filling mold flow in molding parts with micro size or with local tiny structure was investigated. Sheet parts with micro cylindrical array structure were taken as the research object. For two kinds of polymer materials, high-density polyethylene (HDPE) and polypropylene (PP), the micro injection mold which integrated the technologies of vacuum exhaust and ultrasonic vibration was used to study the change of micro cylindrical fillet curvature radius with and without ultrasonic field and under the condition of varying process parameters and ultrasonic power. Without ultrasonic field, raising temperatures of melt and mold and increasing injection rate could decrease the fillet radius of curvature for the micro-column of the two polymer materials. While the fillet radius of curvature for the micro-column could further decrease with ultrasonic field, thereby improving the filling quality of parts. Meanwhile, no matter whether applying ultrasonic field or not, the fillet radius of curvature for the micro-column filled by HDPE polymer material was significantly smaller than that by PP polymer material.
    Hydrothermal preparation of Yb-P-TiO2 nano-photocatalyst from TiCl4 hydrolysis and synergetic mechanism of co-doping
    JIANG Hongquan, LI Zhenyu, WANG Xuefeng, LI Jingshen, WANG Qiaofeng
    2014, 65(12):  5030-5038.  doi:10.3969/j.issn.0438-1157.2014.12.052
    Abstract ( 319 )   PDF (3023KB) ( 295 )  
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    Mesoporous Yb-P-co-doped anatase-TiO2 nano-sheets were synthesized from TiCl4 hydrolysis by the hydrothermal method. The effect of Yb-P-co-doping on the surface physicochemical properties and photocatalytic activities of TiO2 and its mechanism were discussed based on the results of XRD, TEM, BET, XPS, FTIR, DRS and PL analysis. The photocatalytic activities of as-prepared samples towards the degradation of 4-chlorphenol in aqueous solution under simulated sunlight irradiation followed the order of TiO2 < Yb-TiO2 < P25 < P-TiO2 < Yb-P-TiO2, indicating the synergetic effect by Yb-P-co-doping. The TOC removal rate of 4-chlorphenol solution (20 mg·L-1) in the suspension of Yb-P-TiO2 (0.8 g·L-1) reached 87.6% after simulated sunlight irradiation for 120 min, indicating that 4-chlorphenol could be mineralized efficiently. P-doping played a crucial role on both inhibited transformation of TiO2 from anatase to rutile and improvement of surface texture properties. Yb3+ ions could capture photo-generated electrons to form Yb2+, which inturn release electrons to acceptor, such as O2 adsorbed on the surface to produce ·O2-, thus effectively inhibiting recombination of photo-generated charge carriers. The improved light absorption property of Yb-P-TiO2 was attributed to narrowing band gap owing to the cooperative effect of energy levels hybridized by the 3p orbits of P atoms and the 2p orbits of O atoms and energy levels of oxygen vaccancies. Yb-P-co-doping could further inhibit recombination of photo-generated electrons and holes, enhancing quantum efficiency, and could further increase the surface hydroxyl, which was in favor of the capture of photo-generated holes and formation of strong oxidative hydroxyl free radicals. All above factors were beneficial to enhance photocatalytic activity of Yb-P-TiO2.
    Morphology structure and mechanical properties of highly filled polypropylene wood-plastic composite prepared by solid state shear milling method
    NIU Zhihai, CHEN Yinghong, BAI Shibing
    2014, 65(12):  5039-5046.  doi:10.3969/j.issn.0438-1157.2014.12.053
    Abstract ( 209 )   PDF (2622KB) ( 243 )  
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    By taking advantage of the excellent multi-functions, including pulverization, dispersion, mixing and stress reaction of the pan-mill equipment and the good compatibilizing effects of the compatibilizer PP-g-MAH, the highly filled polypropylene (PP) wood-plastic composite with 80%(mass) wood flour (WF) having good comprehensive performance was prepared. The effects of pan-milling, compatibilizer and compounding strategy on the particle size distribution, mechanical performance and morphology structure of the PP/WF wood-plastic composite system were investigated. The particle size of the PP/WF composite at different milling cycles presented double-peak distribution. A proper increase in milling cycle was beneficial to further decrease in PP particle size and uniform dispersion of wood flour. With increasing milling cycle, the tensile and flexural properties of the PP/WF composite increased first and then decreased, but the notched impact strength constantly decreased slightly. The introduction of PP-g-MAH and the increase in its content would contribute to remarkable improvement in the mechanical performance of the PP/WF composite and the best flexural modulus occurred at 5% PP-g-MAH. In addition, the mechanical properties of the PP/WF composite prepared by pan-milling were better than those of the material prepared by the conventional mastication compounding method. The change in mechanical properties mentioned above was attributed to improved dispersion of wood flour in PP/WF highly filled composite system caused by pan-milling and remarkable enhancement in compatibility of system caused by the incorporated PP-g-MAH. The involved compatibilizing mechanism of PP-g-MAH was believed to be the mechano-chemical grafting esterification reaction of PP-g-MAH with the hydroxyl groups at the surface of wood flour under the strong shear force field of pan-milling.
    Physico-mechanical properties and heat-resistant mechanism of nano-MH/AF/NBR composite
    WANG Qilei
    2014, 65(12):  5047-5053.  doi:10.3969/j.issn.0438-1157.2014.12.054
    Abstract ( 286 )   PDF (1103KB) ( 329 )  
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    In order to produce a rubber sealing material with satisfactory physical and mechanical properties, heat resistance, and flame retardance, a nano MH/AF/NBR composite material was made by using nitrile butadiene rubber (NBR), aramid fiber (AF), and nano magnesium hydroxide (MH). Physical and mechanical performance, heat resistance, and flame retardance of the composite material were investigated for different proportions of nano MH and AF. Nano MH reinforced the internal structure of the composite material. The bond strength between AF and rubber matrix decreased with increasing amount of AF in the composite. When MH/AF ratio was 20/10,the stress at definite elongation and tensile strength were increased by 4%, and compression set was reduced by 1%. When MH/AF ratio was 30/10, hardness increased to 73 degree. The nano MH/AF composite had good flame retardance and improved thermal stability of NBR. Additionally, the total smoke production of the composite material was reduced. The results established a foundation for further applications using the nano MH/AF/NBR composite material as a sealant.
    Processing parameters optimization of rapid heat cycle molding based on Kriging meta-model and genetic algorithm
    WANG Menghan, LI Yanzhao, XIA Zhizi, CHEN Mingliang, YANG Hai
    2014, 65(12):  5054-5060.  doi:10.3969/j.issn.0438-1157.2014.12.055
    Abstract ( 257 )   PDF (1142KB) ( 372 )  
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    In order to improve the comprehensive quality of high-gloss plastic part, an integrated optimization strategy based on Kriging meta-model and genetic algorithm (GA) was proposed. The optimization strategy was used to optimize the processing parameters of an air-conditioning panel plastics with rapid heat cycle molding (RHCM). Coupled with CAE analysis, the Taguchi method was used to arrange the experimental points. Through the normalization method, linear weighted method and intuitive analysis, it was found that packing pressure, cooling time, melt temperature and heating time were the significant process parameters which affected comprehensive quality of plastic part with RHCM. Then Kriging meta-model was introduced to establish a predictive model between comprehensive quality and the significant process parameters. Besides, GA was used to seek the best result of the predictive model in the feasible solution space. The optimal process parameters were heating time of 36.9 s, melt temperature of 182.9℃, packing pressure of 88.5 MPa, cooling time of 51.3 s. Finally, computer-aided engineering (CAE) analysis and actual production achieved good result, showing that the integrated optimization strategy was feasible and reasonable in processing quality optimization of high-gloss plastic part.
    Preparation of MFI zeolite membranes in fluoride media and separation performance for ethanol/water mixture
    KONG Qingqing, ZHANG Chun, WANG Xuerui, GU Xuehong
    2014, 65(12):  5061-5066.  doi:10.3969/j.issn.0438-1157.2014.12.056
    Abstract ( 404 )   PDF (1421KB) ( 361 )  
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    MFI zeolite membranes were synthesized on seeded yttria stabilized zirconia (YSZ) hollow fiber substrates by using ammonium fluoride as mineralizing agent and tetrapropylammonium bromide as template. The as-synthesized membranes were tested for separation of ethanol/water mixture. The influences of nNH4F/nSiO2 ratio and synthesis time on separation performance were investigated. High-performance MFI zeolite membrane was synthesized at nNH4F/nSiO2=0.8 and synthesis time of 8 h, which showed a permeation flux of 8.2 kg·m-2·h-1 and ethanol/water separation factor of 47. The stability of MFI zeolite membranes in ethanol/water mixture was investigated. No Si—OH was detected on the surface of the as-synthesized MFI zeolite membranes, which could avoid decreased membrane separation performance by the reaction between Si—OH and ethanol.
    Adsorption characteristics of styrene-sodium methacrylate copolymer on imidacloprid particle surface
    HAO Han, FENG Jianguo, CHEN Weitao, LIU Wenjun, WU Xuemin
    2014, 65(12):  5067-5074.  doi:10.3969/j.issn.0438-1157.2014.12.057
    Abstract ( 319 )   PDF (606KB) ( 239 )  
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    A series of styrene-sodium methacrylate copolymer dispersants were prepared, and the effects of molar ratio on the yield and adsorption on imidacloprid particle surface were investigated. The dispersant was the best when molar ratio of two monomers was 0.8. The adsorption kinetics, isotherm and thermodynamics of the best dispersant on imidacloprid particle surfaces were studied. Adsorption layer thicknesses of dispersant at different temperature were determined by XPS. The adsorption process followed the pseudo-second-order kinetic model with a good correlation coefficient. The adsorption process was fitted with the Langmuir isotherm equation better. Thermodynamic parameters indicated that the adsorption was a spontaneous exothermic process, and higher temperature was not beneficial to the adsorption process. DHad < 40 kJ·mol-1 indicated that the adsorption process was physical adsorption. The adsorption layer thickness decreased with temperature increase. By comparison with the adsorption characteristics of other commercial dispersants, styrene-sodium methacrylate copolymer was eligible for the dispersant on water-based formulations of imidacloprid.
    Effect of glycosylation on gel properties of b-conglycinin under macromolecular crowding condition
    WENG Jingyi, QI Junru, ZHANG Xi, KANG Yanhui, FENG Jilu, YANG Xiaoquan, ZHU Jianhua
    2014, 65(12):  5075-5081.  doi:10.3969/j.issn.0438-1157.2014.12.058
    Abstract ( 274 )   PDF (4688KB) ( 297 )  
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    The effect of glycosylation on the aggregation behavior of b-conglycinin (7S) under the macromolecular crowding condition in the liquid system and the influence of covalent attachment of polysaccharide on gelation of b -conglycinin (7S) were investigated. The gel network of the conjugate became orderly and compact at 7S/dextran (mass ratio) of 2:1. First, b-conglycinin-dextran covalent conjugate was prepared via the Maillard reaction under macromolecular crowding condition. Sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE) was used to confirm the formation of covalent conjugate of 7S-dextran. Transglutaminase (TGase) was introduced for gelation to form a covalent network. Dynamic rheological analysis indicated that the addition of dextran increased the degree of crowding in the liquid system, promoting the formation of gel network. The presence of dextran with high concentration and the covalent attachment to b-conglycinin led to phase separation and inhibited extensive protein-protein interactions during the process of TGase cross-linking. Moreover, frequency sweep measurements revealed that the strength of the gel prepared by conjugation was reduced with increasing concentration of dextran. Scanning electron microscopy observation indicated that the network of gel began to transform to lamellar structure with increasing dextran concentration.
    Kinetics of thermal decomposition of epoxy resins modified with phosphorus-containing flame retardant
    TIAN Xiujuan, WANG Zhongwei, YU Qing, GAO Jun
    2014, 65(12):  5082-5089.  doi:10.3969/j.issn.0438-1157.2014.12.059
    Abstract ( 636 )   PDF (2745KB) ( 578 )  
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    Phosphorus-containing epoxy resin was prepared from 2-diphenylphosphonothioic-1,4-diphenol (DPO-HQ, as flame retardant). The thermal stabilities of neat epoxy resin (EP) and flame retardant modified epoxy resin (FR-EP) were studied with thermogravimetric analysis (TGA) at different heating rates. Kinetics model and model-free kinetics (MFK) were established based on TGA data. The serviceability values of model kinetics and model-free kinetics to epoxy resin and flame retardant modified epoxy resin were compared and analyzed. The initial degradation temperature of flame retardant modified epoxy resin slightly decreased with introduction of flame retardant, but the yield of char residue increased. The model kinetics of EP and FR-EP determined by using the Flynn-Wall-Ozawa method and the Coats-Redfern method were not applicable to epoxy resin system. MFK was more suitable to describe and predict the degradation behavior of epoxy resin and flame retardant modified epoxy resin.
    Gel fraction and swelling degree of hollow alginate fiber fabricated by direct writing and crosslinking
    LI Yu, LIU Yuanyuan, LI Shuai, LIANG Gang, ZHANG Yanan, HU Qingxi
    2014, 65(12):  5090-5096.  doi:10.3969/j.issn.0438-1157.2014.12.060
    Abstract ( 318 )   PDF (4490KB) ( 484 )  
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    With sodium alginate as raw material and calcium chloride as crosslinker, a hollow hydrogel fiber was fabricated by direct writing combined with crosslinking, and was used to construct tissue engineering scaffold. Fiber gel fraction and swelling degree directly affect the forming quality of scaffold and laden cell survival. The influence of materials concentration on gel fraction was analyzed by leaching the ungelled part from the fiber. As a control group, alginate beads were prepared with coagulating bath. The requirements of direct writing process, such as gel rate, gel fraction and fiber morphology were satisfied, when the concentration of sodium alginate and calcium chloride were 4% and 3% respectively. With increasing sodium alginate's concentration, equilibrium swelling degree of hollow fiber first decreased and then slightly increased and stabilized finally. With increasing calcium chloride's concentration, swelling degree gradually decreased. Due to smaller diffusion interface, swelling degree of hollow fiber was two to five times higher than the gelled beads, and higher moisture was in favor of the viability and mass transfer for cell laden.