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05 November 2014, Volume 65 Issue 11
    CIESC Journal(HUAGONG XUEBAO)Vol.65 No.11 May 2014
    2014, 65(11):  0-0. 
    Abstract ( 213 )   PDF (4190KB) ( 401 )  
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    Progress of preparing regenerated cellulose fibers using novel dissolution process
    CHEN Jinghuan, WANG Kun, XU Feng, SUN Runcang
    2014, 65(11):  4213-4221.  doi:10.3969/j.issn.0438-1157.2014.11.001
    Abstract ( 410 )   PDF (6275KB) ( 672 )  
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    Research and development of regenerated cellulose fibers prepared from renewable and biodegradable natural cellulose is of great significance to making full use of cellulose resources and promoting sustainable development of fiber industry. Recently, novel regenerated cellulose fibers have been prepared from ionic liquids and alkaline solution systems due to their excellent solubility for cellulose. The preparation processes of these fibers are comparatively simple and cause less pollution than that of the traditional techniques. The fibers produced by the ionic liquids method have excellent mechanical properties, while the fibers produced by the alkaline solution method are comparatively inexpensive. The recent developments of novel regenerated cellulose fibers using ionic liquids and alkaline solution systems as solvents are reviewed, including types of solvents, selection of raw materials, preparation methods and mechanical properties of the fibers. The effects of various factors on the physical properties of novel fibers are also summarized and compared. The challenges and future research trends of novel regenerated cellulose fibers are suggested.
    2-D hydrodynamic model of bubble column based on lateral-force balance
    LI Zhaoqi, WANG Lijun, GUAN Xiaoping, CHENG Youwei, LI Xi
    2014, 65(11):  4222-4230.  doi:10.3969/j.issn.0438-1157.2014.11.002
    Abstract ( 344 )   PDF (1776KB) ( 283 )  
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    A 2-D axisymmetric hydrodynamic model of bubble column was developed, by considering lift force and turbulent dispersion force on bubbles as main mechanism of stable distribution of gas holdup. A commercial code Fluent 6.3 was used for calculation, and the model gave a stable 2-D flow pattern, in which distributions of gas holdup and liquid velocity were in good agreement with experimental data. The model correctly demonstrated the influence of superficial gas velocity (0.12—0.62 m·s-1) and column diameter (ø200 mm, ø500 mm, ø800 mm) on flow pattern. Furthermore, hydrodynamic variables predicted by the model in larger scale columns agreed with published empirical correlations.
    Flow characteristics of slug flow in helical rectangular channel
    LIU Xianfei, XIA Guodong, YANG Guang
    2014, 65(11):  4231-4237.  doi:10.3969/j.issn.0438-1157.2014.11.003
    Abstract ( 512 )   PDF (2303KB) ( 733 )  
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    Experimental investigations on slug flow were carried out in horizontal helical rectangular channel by using high speed flow visualization. Evolution of slug in the whole helical rectangular channel was presented and the fine features of slug flow in different positions were illustrated. The slug characteristics changed along the axial direction due to the combined effects of gravitational and centrifugal force. Based on the experimental data, slug velocity, slug frequency and length distribution in different positions were given. The present topography measurement illustrated the evolution features of liquid film thickness, which was determined by the effect of centrifugal force and gravity. Liquid film falling velocity decreased as the slug moved upward and was visibly increasing in the downward flow.
    Mass transfer analogy model of PM2.5 collection on interface of gas-liquid cross-flow through staggered falling film array
    LI Ji, ZHENG Zhijian, ZHU Jiahua, XIA Sulan, LI Yong, WEN Hao
    2014, 65(11):  4238-4245.  doi:10.3969/j.issn.0438-1157.2014.11.004
    Abstract ( 474 )   PDF (2520KB) ( 408 )  
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    According to the pseudo-homogeneous fluid performance of aerosol particles, a mass transfer analogy model was proposed for PM2.5 collection on the interface of gas-liquid cross flow. With the mechanism analysis on the particle transport behavior analogized to fluid convective heat transfer, which is mainly affected by the Schmidt number (Sc) and its exponent m, an analogous equation of Sherwood number (Sh) of particle transfer was derived for PM2.5 collection through a staggered falling film array (SFFA), based on a widely used equation of Nusselt number (Nu) of convective heat transfer over the staggered tube bundles. From the analogous equation of Sh, a model for prediction of PM2.5 collection efficiency was deduced with the exponent m as the model parameter. The value of m was obtained to be 0.808 via regression analysis of experimental data of PM2.5 collection efficiencies measured in a SFFA consisting of 20 (line)×90 (row) falling film cylinders with diameter of 3 mm. In the range of Reynolds number from 50 to 650, the deviation between the model prediction of PM2.5 mass transfer Sh and the experimental data is within ±20%.
    Numerical simulation of R32 condensation heat transfer in horizontal circular microchannel
    LIU Na, LI Junming
    2014, 65(11):  4246-4253.  doi:10.3969/j.issn.0438-1157.2014.11.005
    Abstract ( 409 )   PDF (940KB) ( 357 )  
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    Condensation heat transfer of R32 in a horizontal circular microchannel with the inner diameter of 1 mm is numerically simulated with VOF model. The inlet saturation temperature of R32 is 40℃ and the wall temperature is 30℃. The vapor and liquid phases are assumed to be turbulent and laminar, respectively, and the effects of gravity and surface tension are considered. The simulation results show that the vapor quality decreases nearly linearly along the tube and reaches 0.62 at the outlet of the channel, and the liquid film thickness at the top of the tube increases first and then maintains almost constant while the liquid film thickness at the bottom of the channel increases consistently along the channel. As the thermal conductive resistance of the liquid film is dominant in condensation heat transfer, the heat transfer on the top surface tube is stronger than that on the bottom surface. The liquid film on the top surface flows to the bottom of the tube due to the effect of gravity. The results show that the gravity effect cannot be neglected when the hydraulic diameter of channel is 1 mm. Axial velocity distribution of the liquid film is linear with the vapor quality. Vapor-liquid interface velocity on the top surface in the tube increases first and then decreases a little along the channel while interfacial velocity on the bottom increases consistently. Simulated heat transfer coefficients increase with vapor quality, and the simulation results are lower than the experimental results in the overlapped vapor quality region while the deviations are still within the experimental error.
    Performance analysis on small-scale turbine used in ORC system at different rotational rates
    XIA Lijun, PEI Gang, LI Jing, HU Mingke, JI Jie
    2014, 65(11):  4254-4261.  doi:10.3969/j.issn.0438-1157.2014.11.006
    Abstract ( 454 )   PDF (792KB) ( 551 )  
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    Few studies have focused on the overall performance and internal flow field of small-scale turbine under off-design conditions in an organic Rankine cycle (ORC) system. The small-scale turbine of an ORC system is often used at variable rotation rates for renewable energy and waste heat utilization. The 3D flow field of a small-scale, radial-axial flow turbine impeller is simulated with CFX software and verified by experimental data and design data, which uses R123 as work fluid. The variations of thermal efficiency and isentropic efficiency of impeller with the rotating rate are provided. The leaving-velocity loss of the turbine is the main cause of lower thermal efficiency at a low rotation rate. A revised equation for calculating the power output of a small-scale turbine under the off-design condition, which considers the change in the kinetic energy between the inlet and outlet of the turbine, is also proposed. The flow direction of working fluid should be considered when calculating the leaving-velocity loss at the outlet of the turbine. The isentropic efficiency of the turbine is evidently low at less than 20000 r·min-1, whereas the kinetic energy difference between the inlet and outlet of the turbine impeller is close to 0 at 60000 r·min-1.
    Numerical simulation of gas-solids two-phase flow field of built-in fourth stage cyclone separation system in FCCU
    WANG Rui, WANG Jianjun, ZHAO Yan, JIN Youhai
    2014, 65(11):  4262-4270.  doi:10.3969/j.issn.0438-1157.2014.11.007
    Abstract ( 316 )   PDF (2889KB) ( 337 )  
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    The Reynolds stress model was used to simulate gas-solids flow field of built-in fourth stage separation cyclone system in FCCU. Cross flow existed at the bottom of the dust hopper in the cyclone separator, which was not favorable for particle discharge. Although blowdown on the top of the dust storage tank could help separator discharge, it also increased the chance of particles escaping from the balance tube, lowering separation efficiency. The movement trajectory of particles in the system included trapped in the dust hopper of the dust storage tank, escaping from the vortex finder and the balance tube. In order to reduce particles escaping from the balance tube, adding a cone baffle in the dust storage tank could be an effective way. Particle concentration was higher at the top of the annular space and the bottom of the dust hopper, causing wall wear out. The built-in fourth stage separation cyclone system had an advantage of resolving catalyst loss.
    Influence of offset angle on refrigeration efficiency of gas wave refrigerator and prediction for optimal offset angle
    LIU Peiqi, XU Siyuan, WANG Zewu, LIU Sheng, HU Dapeng
    2014, 65(11):  4271-4277.  doi:10.3969/j.issn.0438-1157.2014.11.008
    Abstract ( 433 )   PDF (718KB) ( 267 )  
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    The offset angle of gas wave refrigerator is one of the most important parameters affecting the refrigeration efficiency. In this study, the optimal offset angle corresponding to the opening state of oscillating tube is analyzed by numerical methods. The numerical results, theoretical calculations and experiments are combined to explore the method for predicting the optimal offset angle and analyze the influence of offset angle on the refrigeration efficiency. Under given condition, when the shock wave reaches the end of the oscillating tube and half of the tube is contacted with the high temperature port at the same time, the offset angle of gas wave refrigeration is the optimal. The optimal offset angles determined by experimental data have the same trends with theoretical calculations, increasing with the angle and rotation speed, but the values differ considerably from the theoretical results. The optimal offset angles calculated by numerical simulation agree well with the experimental results, with the error less than 1%. When the rotation speed of gas wave refrigeration is lower than that with the optimal offset angle, the refrigeration efficiency decreases linearly with the reduction of rotation speed. When the rotation speed is faster than that speed, the refrigeration efficiency increases linearly with the reduction of rotation speed. With the change of rotation speed, the absolute values of linear fitting curve slope of rising and falling of the refrigeration efficiency is almost equal, which lies in the range of 0.009—0.012.
    Turbulence intensity of real tangential velocity in circular pipe
    CAI Xiangli, LI Pei, YANG Zhiyong, HUANG Lei, WEI Yaodong
    2014, 65(11):  4278-4284.  doi:10.3969/j.issn.0438-1157.2014.11.009
    Abstract ( 288 )   PDF (1023KB) ( 289 )  
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    The real tangential velocity of swirling flow in a circular pipe with diameter 300 mm and length 2000 mm was measured by using hot wire anemometry (HWA), and analysis emphasized on turbulence intensity of the tangential velocity with the effect of oscillation of swirling flow. The real tangential velocity contained high frequency turbulent fluctuation velocity and low frequency fluctuation velocity. The real tangential velocity fluctuated obviously in the center region of the circular pipe, but fluctuated little near the wall of the circular pipe. By analyzing probability density of the real tangential velocity of swirling flow, fluctuation of the real tangential velocity changed greatly along the radial direction. This fluctuation was not only affected by turbulent fluctuation, but also by oscillation of swirling flow. Oscillation of swirling flow resulted in the phenomenon that turbulence intensity of the tangential velocity in the center region was higher than that near the wall.
    Thermal energy storage characteristics of sand as filler material for solar thermocline tank
    YANG Yongping, HAN Jingxiao, LI Peiwen, HOU Hongjuan, XU Ben
    2014, 65(11):  4285-4292.  doi:10.3969/j.issn.0438-1157.2014.11.010
    Abstract ( 511 )   PDF (1212KB) ( 395 )  
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    The feasibility of sand at various grain sizes as filler material for solar sensible heat thermal energy storage (TES) was investigated. An indirect contact sensible heat TES experiment setup was built. The TES section is a cylindrical tank, which is embedded with 19 stainless tubes arranged like a hexagonal honeycomb. Air was chosen as the heat transfer fluid to flow inside the tubes and carry heat, while the sand in the tank contacts the outside of tubes. Four types of sand: silver sand, medium sand, filter sand and coarse sand, were selected. The results show that voidage is the determining factor for the TES performance rather than density or grain size. Coarse sand is the best among the four types. For materials such as sand whose basic thermal properties only vary a bit, the change of charge temperature can hardly affect the TES performance. When using air as the heat transfer fluid, the TES efficiency is relatively lower. To enhance heat transfer, a lower air velocity or longer tube length is needed. The simplified 2-D simulation results match well with the experimental results and can be used for the prediction of large scale TES tank performance.
    Numerical simulation and experiments on submerged supersonic gas jets
    WANG Chao, WANG Jianfeng, SHI Honghui
    2014, 65(11):  4293-4300.  doi:10.3969/j.issn.0438-1157.2014.11.011
    Abstract ( 338 )   PDF (10391KB) ( 1269 )  
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    Underwater submerged supersonic gas jet is a gas jet from the orifice or nozzle into water at supersonic speed, which diffuses in water flow and causes complex gas-water mixing and interface instabilities. Firstly, the flow field of the 3-dimensional submerged supersonic gas jet was recorded by a high speed camera in the experiment. Secondly, Ax-symmetric model was established for the experimental case by the VOF method. The numerical and experimental results showed early evolution of bubble motion of the jet and evolution process of a bubble, including generating, growing, being broken by the next one, bulging and back-attack etc. The jet flow field structures, such as distribution of pressure and velocity, Mach number in the flow field during injection were analyzed by numerical simulation. Complex shock wave/expansion wave cell structures existed in the field of the submerged jets, influencing the parameters in the flow fields and leading to the phenomena, such as bulging, back-attack. The results of numerical simulation agreed well with the results of experiment.
    Simulation of drag reduction of aqueous foam on heavy oil flow boundary layer
    JING Jiaqiang, SUN Jie, ZHAO Hongyan, DUAN Nian, ZHOU Yinuo, XU Quanxin
    2014, 65(11):  4301-4308.  doi:10.3969/j.issn.0438-1157.2014.11.012
    Abstract ( 387 )   PDF (2180KB) ( 317 )  
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    According to the eccentricity of core oil flow in water-annulus transport of heavy oil, a simulated experiment for heavy oil flow boundary layer under the action of aqueous foam system-2 (AFS-2) (foam quality 50%) was proposed. A corresponding pipe flow simulated device and a system of foam generating, injecting and foam layer generating were designed and built. Flow resistance characteristics of heavy oil simulated by 201 methyl silicone oil under the action of aqueous foam in horizontal pipe were determined experimentally, and the influence of velocities and flow ratios of foam and silicone oil on silicone oil flow patterns and drag reduction was analyzed. Based on the hypothesis on complex boundary layer of upper foam-lower foam drainage film, a model for predicting pressure drop of silicone oil-foam-foam drainage film core-annular flow in horizontal pipe was established. At room temperature 20℃, drag reduction efficiency was above 70% when flow ratios of foam and silicone oil were between 0.2 and 0.5, and its mechanism of drag reduction could be the complex isolating-lubricating layer of upper foam-liquid film between oil and pipe wall. The predicted values were in good agreement with the experimental data, and relative errors were between -17.55% and 9.76%.
    Regression algorithm based on minimum variance and its application in heat exchanger measurement
    LENG Xueli, QIU Yan, TIAN Maocheng, LI Wei
    2014, 65(11):  4309-4314.  doi:10.3969/j.issn.0438-1157.2014.11.013
    Abstract ( 268 )   PDF (1794KB) ( 256 )  
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    Correlation regression methods for heat exchanger have been developed in last several years, such as the method based on equal flow Reynolds number, the method based on equal flow velocity, and the Wilson plot technique, improvements of which contribute outstandingly in measuring heat transfer equipment. The defect in those methods is as follows. The methods based on equal flow Reynolds number and flow velocity restrict the flow conditions, duct structure and flow media in two ducts. The Wilson plot technique demands the exponent of Reynolds number. A new method is presented in this paper, which is similar to the Wilson plot technique but avoid above restrictions through searching proper coefficient and exponent in the correlation by examining the minimum variance in different fitting consequence, giving accurate heat transfer coefficients on the fixed side. The relation between two ducts is the thermal resistances in series. The method resolves the correlation fitting technique with a dichotomy, which is more accurate than linear regression analysis commonly used. The method is validated by simulated data first and then by experimental data. The result shows that the method is reasonable.
    Effect of nano-particles and relevant dispersants on surface tension and boiling temperature of LiBr aqueous solution
    XIE Guozhen, WANG Liangliang
    2014, 65(11):  4315-4320.  doi:10.3969/j.issn.0438-1157.2014.11.014
    Abstract ( 477 )   PDF (486KB) ( 387 )  
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    Surface tension and boiling temperature were determined with a contrastive experimental method for LiBr aqueous solutions without and with nano-particles or dispersants added in a same quantity of recipe. The influence of different dispersants and nano-particles on properties of LiBr aqueous solution was conjectured and analyzed qualitatively through the molecular structure of dispersant and the external contour and size of nano-particles. It is found experimentally that the surface tension of solution reduces significantly with dispersants added and its boiling temperature decreases correspondingly. The boiling temperature is increased with nano-particles added because the particles will fill the micro-pits on the heating surface. The boiling temperature of LiBr aqueous solution added with nano-particles and its relevant dispersants have a great influence on the positive effect of lower surface tension and negative effect that nano-particles fill the pits.
    Ice nucleation of ice thermal storage air-condition
    ZHANG Xuelai, MENG Xianglai, ZHAO Qunzhi, LI Chunlei
    2014, 65(11):  4321-4324.  doi:10.3969/j.issn.0438-1157.2014.11.015
    Abstract ( 620 )   PDF (1583KB) ( 467 )  
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    Experiment on different depth of water tank supercooling degree was carried out. The results show that the supercooling degree of the upper water in ice storage tank is higher. In order to reduce the supercooling degree of the water and energy consumption of the chiller, different nucleation additives are tested and it is found that adding nano-copper oxide can reduce the supercooling degree and improve the ice storage efficiency. Appropriate mass fraction of copper oxide nanoparticles is obtained under a certain quality dispersant. When the ice-making temperature is -5℃, 0.10% mass fraction copper oxide suspension is at the top. Supercooling degree of water is also associated with the temperature difference of heat transfer medium. The higher the difference in temperature is, the smaller the supercooling degree.
    Photocatalytic planar microreactor of copper ion doped titanium dioxide
    LIN Cheng, LIU Mingyan
    2014, 65(11):  4325-4332.  doi:10.3969/j.issn.0438-1157.2014.11.016
    Abstract ( 443 )   PDF (907KB) ( 424 )  
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    Applying microreactor technology to photocatalytic reactions is a novel and potential technical innovation. Photocatalytic planar microreactors were fabricated by metal etching technology, and copper ion doped TiO2 was immobilized as coatings by the sol-gel method. X-ray diffraction, scanning electron microscope and UV-visible diffuse reflection were used for characterization of photocatalyst. The microreactors were tested for the degradation of methyl orange and the optimal doping concentration of copper ion was found to be 0.04% (mole ratio to Ti). The degradation ratio of methyl orange with an initial concentration of 10 mg·L-1 could reach 45% within 90 s in the microreactor. Degradation ratios of methyl orange in microreactors under controlled irradiation were measured, and the copper ion doped photocatalytic microreactors showed better utilization of irradiation energy. The study of kinetics illustrated that the degradation of methyl orange in the microreactors was a first order reaction of incomplete oxidation with a much greater rate constant (k) comparing to regular reactors. The rate constant increased with the decreasing of initial concentration (C0), and there was a good linear relationship of lnk and lnC0.
    Synthesis of propylene carbonate from urea and 1,2-propylene glycol over MnO2/γ-Al2O3 catalyst modified by NaOH
    DU Zhiping, LIN Zhikun, CHEN Fangsheng, HU Xingxing, DING Yigang, CHI Ru'an, WU Yuanxin
    2014, 65(11):  4333-4339.  doi:10.3969/j.issn.0438-1157.2014.11.017
    Abstract ( 276 )   PDF (1520KB) ( 251 )  
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    MnO2/γ-Al2O3 catalyst was prepared by ultrasonic impregnation and modified by alkali or salt. The modified MnO2/γ-Al2O3 was characterized by X-ray diffraction (XRD), temperature-programmed desorption of CO2(CO2-TPD). Catalytic performances were investigated in urea alcoholysis to propylene carbonate (PC). The activity of MnO2/γ-Al2O3 catalyst modified by NaOH was the best. At the same time, calcination temperature, calcination time and amount of NaOH affected the quantity and intensity of basic activity centers on the surface of the modified catalyst. The increase of moderately basic activity center was the main reason for the catalyst activity improvement after modification. When the MnO2/γ-Al2O3 catalyst was modified by 10% NaOH, and calcined at 400℃ for 2 h, the quantity of moderately basic activity center on the surface was the most, which led to the highest activity. Yield and selectivity of PC were up to 86.9% and 91.8%, respectively.
    Production of bio-oil by catalytic pyrolysis of Nannochloropsis sp. over renewed suface CaO catalysts
    YANG Lin, ZHANG Xiuli, YANG Ya, WANG Xuyun, XU Xiufeng, GUO Qingjie
    2014, 65(11):  4340-4346.  doi:10.3969/j.issn.0438-1157.2014.11.018
    Abstract ( 326 )   PDF (2254KB) ( 296 )  
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    The surface of calcium oxide (CaO) was renewed by using hydration-calcination and thermal calcinations methods, respectively. The structure and property of renewed CaO was characterized by BET, XRD, SEM and CO2-TPD techniques. Meanwhile, the catalytic pyrolysis of Nannochloropsis sp. was investigated in a fixed-bed reactor. It is shown that two preparation methods for CaO obviously increase the specific surface area, meso-pore numbers, and pore volume. The renewed surface CaO catalysts were of typical face-centered structure and of higher catalyst activity, and could improve bio-oil product quantity. The yield of bio-oil produced on the hydration-calcination CaO was 28.65%, which was of higher calorific value (38.600 kJ·g-1), lower kinetic viscosity (8.011 mm2·s-1), and lower moisture content (2.49%). The main ingredients of bio-oil from catalytic pyrolysis of Nannochloropsis sp. were C12—C17 saturated normal alkanes, which are more suitable for being upgraded to bio-diesel.
    Removal of oxygenates in aqueous phase product of F-T process by catalytic hydrogenation over Ru catalyst
    CHEN Lungang, LIU Yong, DING Mingyue, ZHANG Xinghua, LI Yuping, ZHANG Qi, WANG Tiejun, MA Longlong
    2014, 65(11):  4347-4355.  doi:10.3969/j.issn.0438-1157.2014.11.019
    Abstract ( 312 )   PDF (2600KB) ( 318 )  
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    Removal of oxygenates in aqueous phase product of Fischer-Tropsch (F-T) process was studied by the catalytic hydrogenation over supported Ru catalysts. The catalytic performance of several Ru catalysts supported on different metal oxides such as ZrO2, TiO2, SiO2 and γ-Al2O3 was investigated. In the catalytic hydrogenation processes, aldehydes, ketones and esters are more readily to be transformed than carboxylic acid and alcohol. The Ru/ZrO2 and Ru/TiO2 catalysts exhibited excellent hydrogenation activity, and under the conditions of 200℃, 9.8 MPa pressure and 3.0 h-1 WHSV, the carboxylic acids, aldehydes, alcohols, ketones and esters all are transformed to C1—C6 alkanes with overall conversion of above 92%. However, the Ru/Al2O3 catalyst displays the lowest activity towards alcohols with below 30% of conversion at the same conditions, although other oxygenates, including carboxylic acids, aldehydes, ketones and esters, are transformed with considerable conversion of above 87%, indicating that the Ru/Al2O3 catalyst was of selectivity for the conversion of oxygenates and the most of alcohols can not be transformed. The results from H2-TPR and NH3-TPD reveal that the synergy between metal and alumina is conductive to the hydrogenation of carboxylic acids and inhibits the hydrogenation-decarbonylation of alcohols. On the contrary, the catalysts with weak metal-support interaction and low acidity improve the hydrogenation activity for carboxylic acids and alcohols. However, there was a good stability of 400 h for Ru/Al2O3 catalyst, although the degeneration of catalytic activity was also observed after running 400 h. The results from X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 physisorption show that the change of textural and structural properties is the key factors for activity degeneration of Ru/Al2O3 catalyst, because of the transformation of γ-alumina to boehmite and of the great decrease of surface area from 197 m2·g-1 to 21 m2·g-1 and loss of porosity.
    Effect of pretreatment of carbon support on electrocatalytic properties of Pt/C nanocatalysts
    CAI Yuanrong, HUANG Rui, HUANG Long, RAO Lu, CHEN Shengpei, ZHOU Zhiyou, SUN Shigang
    2014, 65(11):  4356-4362.  doi:10.3969/j.issn.0438-1157.2014.11.020
    Abstract ( 330 )   PDF (4903KB) ( 595 )  
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    Carbon supported Pt nanocatalysts (Pt/C) are widely used in fuel cells. In this work, three kinds of Pt/C catalysts were successfully prepared via a chemical reduction method by using carbon black pretreated with different methods, i.e., HNO3-pretreated carbon (Pt/C-HNO3), H2O2-pretreated carbon (Pt/C-H2O2) and unpretreated carbon (Pt/C). The morphologies and properties of the as-prepared Pt/C catalysts were characterized by SEM, HR-TEM, CV and COad stripping. Pt nanoparticles were dispersed well in these three Pt/C catalysts with average particle size of 3.4, 3.9 and 4.5 nm respectively. HR-TEM observation indicated that Pt/C-HNO3 possessed high-density of step atoms and COad stripping experiments showed that Pt/C-HNO3 exhibited the best anti-poisoning property. Comparing the catalytic activities of three as-prepared Pt/C catalysts toward ethanol electrooxidation with commercial Pt/C catalyst (Pt/C JM) showed that the as-prepared catalysts exhibited higher activity and stability than those of Pt/C JM and the order was Pt/C-HNO3>Pt/C-H2O2>Pt/C>Pt/C JM. Especially for Pt/C-HNO3, its activity and stability were 1.5 times and 1.9 times of those of Pt/C JM respectively.
    Experimental study on catalytic ignition of n-C4H10/H2/air mixtures
    ZHONG Beijing, YU Yawei, XIONG Pengfei
    2014, 65(11):  4363-4367.  doi:10.3969/j.issn.0438-1157.2014.11.021
    Abstract ( 221 )   PDF (509KB) ( 225 )  
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    An experimental study on catalytic ignition of n-C4H10/H2/air mixtures in the Pt-coated catalyst surface was conducted. Hydrogen had not only thermal, but also chemical effects on the catalytic ignition of the n-C4H10/air mixtures. The chemical catalytic ignition temperature of the combustible mixtures was obviously lower than thermal ignition when chemical effect was dominant. However, chemical catalytic ignition occurred only when hydrogen content in the combustible mixtures was greater than a critical value. The critical value and the catalytic ignition temperature were related to equivalence ratio of the combustible mixtures.
    Experiment of polyvinyl chloride plastic dechlorination process under condition of minimum secondary reaction
    LUO Jia, GUI Ben, WAN Wenjun, ZHANG Xi, WANG Wenxia, QIAO Yu
    2014, 65(11):  4368-4375.  doi:10.3969/j.issn.0438-1157.2014.11.022
    Abstract ( 320 )   PDF (1685KB) ( 247 )  
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    Pyrolysis experiments of polyvinylchloride (PVC) were performed using a wire-mesh reactor. Non-condensing gases were collected at a heating rate 1—1000 K·s-1 with temperatures from 300℃ to 800℃ and a holding time from 0 to 120 s. EPA-method 26A was employed to determinate the concentrations of both Cl2 and HCl. The results showed that the release of HCl and Cl2 increased continually with increase of temperature and reaction time. Lower heating rate could make the total gas yield increase but do not change the chlorine distribution. Cl2 seemed as an accompanied product during HCl release, which indicated that a bunch of free Cl radicals were involved in PVC thermal degradation. The results confirmed that the pyrolysis process of PVC plastic followed the free radical chain mechanism. Lastly, it was further indicated, by the analysis of PVC pyrolysis tar, that the products obtained at the first stage of PVC pyrolysis were straight-chain polyenes rather than ring structure compounds, i.e. occurring of cyclization reactions seemed impossible at the phase.
    Rheokinetics of organic zirconium crosslinked AM/DMAM/AMPS terpolymer
    YAN Fangfang, FANG Bo, LU Yongjun, HOU Xiangqian, QIU Xiaohui, PENG Fei, WANG Jinshuang
    2014, 65(11):  4376-4382.  doi:10.3969/j.issn.0438-1157.2014.11.023
    Abstract ( 463 )   PDF (638KB) ( 432 )  
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    A high temperature resistant polymer gel with lactic acid/ glycerine organic zirconium as crosslinking agent and a polymer [a kind of acrylamide (AM)/N,N-dimethyl acrylamide (DMAM)/2-acrylamide-2-methyl propane sulfonic acid (AMPS) terpolymer of high temperature resistance] as thickening agent was prepared. The rheological properties (viscoelasticity and thixotropy) and crosslinking rheokinetics of the polymer gel were studied. The changes of viscosity and viscoelastic modulus with time in the crosslinking process were obtained. The effects of shear rate and temperature on gel formation were investigated and a crosslinking rheokinetics model was established. The polymer gel had obvious viscoelasticity and thixotropy. Viscosity was maintained at 176.8 mPa·s after the crosslinked polymer gel was sheared at 170 s-1 for 120 min at 180℃. The high temperature resistant fracturing fluid gel which could endure 180℃ was obtained. The first order rheokinetics model would well describe the rheokinetics of polymer crosslinking process and the model parameters could have well-defined and reasonable significance.
    TD24 determination for mono-nitration products of toluene
    ZHOU Yishan, CHEN Liping, CHEN Wanghua, YANG Ting, ZHANG Caixing, YIN Ruili
    2014, 65(11):  4383-4391.  doi:10.3969/j.issn.0438-1157.2014.11.024
    Abstract ( 1050 )   PDF (819KB) ( 545 )  
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    To determine the temperature of sample 1 (toluene mono-nitration crude product: mononitrotoluene with a little mixed acid) and sample 2 (pure mononitrotoluene product, MNT) TD24, at which the required time to reach maximum rate of temperature rise under adiabatic condition is 24 hours, and to obtain the thermal decomposition characteristics of these products, differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC) were employed to test the thermal behaviors of the two samples. By kinetic analysis for dynamic data obtained by DSC in dynamic mode, the TD24 determined for samples 1 and 2 are (246.1±4.5)℃ and (257.9±3.6)℃, respectively. As a comparison, the values of TD24 for sample 1 and 2, determined by ARC under adiabatic condition, are 241.5℃ and 256.4℃, respectively. Therefore, the TD24 values derived from dynamic data are in good agreement with those by ARC, which means that the results derived from DSC are of large reliability and can be used as a reference for engineering applications. Meanwhile, a comparison for the results of sample 1 and 2 indicates that the thermal hazard of MNT with a little mixed acid is higher than that of pure one.
    Curing process and kinetics of CMC/E44/DDM systems
    DONG Hongxing, ZHAO Qingchen, ZHANG Jin, CHEN Ye, YUE Guojun, LIU Wenxin, LIU Jinsong, LIU Lijia, ZHANG Chunhong
    2014, 65(11):  4392-4399.  doi:10.3969/j.issn.0438-1157.2014.11.025
    Abstract ( 403 )   PDF (578KB) ( 351 )  
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    The influence of sodium carboxy methyl cellulose (CMC) on the curing process of epoxy resin E44 with 4,4'-diamino diphenyl methane (DDM) was studied by using infrared spectra and thermal analytical methods. Infrared spectra indicated that the CMC contributed to forming more polyether structures during the curing process. The study of non-isothermal curing kinetics by differential scanning calorimeters (DSC) showed that CMC accelerated curing reaction of E44/DDM and reduced reaction activation energy in the initial reaction stage. The iso-conversional method and the autocatalytic model were used to analyze the curing process of E44/DDM and CMC/E44/DDM systems respectively. A kinetic model was built. The changes of activation energy (E) versus conversion (a) were obtained by the Starink's iso-conversional method for E44/DDM system and CMC/E44/DDM systems respectively. The activation energy (E) of E44/DDM system was reduced obviously with increasing conversion. When CMC content was the same, activation energy of the CMC system with high molecular weight was higher than that with low molecular weight. However, for the CMC/E44/DDM system, as the degree of conversion increased, variation of E was not obvious. The SB (m, n) autocatalytic kinetic model was used to describe the curing reaction process of the studied system. The model parameters were calculated by using the Levenberg-Marquardt method. The SB model showed a good agreement with experimental data of CMC/E44/DDM system. However, the SB model showed a relatively bad agreement with experimental data of E44/DDM system. An E variable autocatalytic kinetic model was proposed to describe the curing process of E44/DDM system due to the obvious change of activation energy and the model parameters calculated with the Levenberg-Marquardt method. Compared with the SB model, this model showed a better agreement with the experimental data of E44/DDM system. The results of the research provide theoretical basis for improvement of manufacturing process and optimization of processing window.
    Quinoline degradation and mechanism in catalytic wet peroxide oxidation system
    ZOU Han, WANG Shutao, YOU Hong, WANG Zhishen, WANG Weiqing
    2014, 65(11):  4400-4405.  doi:10.3969/j.issn.0438-1157.2014.11.026
    Abstract ( 380 )   PDF (724KB) ( 288 )  
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    In order to study the removal and degradation mechanism of quinoline in catalytic wet peroxide oxidation (CWPO) system, a series of experiments were conducted over CuO-FeOx/γ-Al2O3 catalyst. The influence of reaction temperature, initial pH, dosage of H2O2 and amount of catalyst were investigated, and the role of and degradation pathways of quinoline were analyzed. CWPO had good removal efficiency for quinoline. A complete quinoline conversion and 88.34% total organic carbon (TOC) removal were achieved in 60 min with initial pH of 7, 29.15 mmol·L-1 of H2O2 and 4 g·L-1 of catalyst at 80℃.·OHoxidation played a dominant role in quinoline degradation in CWPO system, and its average production rate was 1.69×10-6 mmol·L-1·min-1. Under neutral and acidic conditions, quinoline degradation in CWPO system followed different pathways, and generated pyridine-based or benzene-based intermediate products.
    Start-up of CANON reactor with modified polyethylene carrier and its performance
    FU Kunming, ZHANG Jie, CAO Xiangsheng, LI Dong, ZUO Zaorong, WANG Huifang
    2014, 65(11):  4406-4412.  doi:10.3969/j.issn.0438-1157.2014.11.027
    Abstract ( 443 )   PDF (555KB) ( 229 )  
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    A CANON reactor with modified polyethylene carrier was started up by seeding sludge from another mature CANON reactor and using artificial inorganic ammonia-rich waste water as influent. To accelerate ANAMMOX bacteria cultivation, the start-up was under anaerobic conditions first to avoid dissolved oxygen inhibition on ANAMMOX bacteria, and then under aerobic conditions. The reactor was first under anaerobic conditions to start ANAMMOX process at room temperature [(20±5)℃] in first 300 days, however, total nitrogen removal load was only 0.12 kg·(m3·d)-1, which meant failure of ANAMMOX. When temperature was increased to 30℃, 30 days later, total nitrogen removal load was up to 0.23 kg·(m3·d)-1. Then anaerobic conditions was changed to aerobic conditions, and total nitrogen removal load was up to 1.01 kg·(m3·d)-1, while nitrogen removal efficiency was 77.61%, and average variation ratio of nitrate and nitrogen (δNO3--N/δTN) was 0.122, close to theoretical value 0.127, showing both good stability of nitritation and good nitrogen removal. Adopting the way of anaerobic stage first and then aerobic stage could not accelerate ANAMMOX bacteria cultivation as expected, and modified polyethylene carrier was not a suitable carrier to start ANAMMOX process under anaerobic conditions. However, once the reactor was successfully started up, aeration could be saved, though it might perform unstably. Modified polyethylene carrier was suggested to combine with UASB reactor to keep bacteria.
    Experimental study on mercury capture using non-carbon sorbents in 100 MW coal-fired power plant
    DU Wen, YIN Libao, ZHUO Yuqun, XU Qisheng, ZHANG Liang, CHEN Changhe
    2014, 65(11):  4413-4419.  doi:10.3969/j.issn.0438-1157.2014.11.028
    Abstract ( 556 )   PDF (702KB) ( 425 )  
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    The mercury removal from the flue gas discharged from a 100 MW coal-fired power plant in China by non-carbon sorbents CuCl2 impregnated alumina and zeolite were experimentally investigated in this paper. When the sorbent were added into, the mercury speciation in flue gas across ESP was directly sampled and analyzed using EPA 30B standard method. The effect of injection rate was studied. The mercury balances measured on-site were between 77.1%—111.5%, and the results of mercury balance after correction suggested that the rates of mercury removal increased with increase of injecting amounts, and was up to 30.6% for modified alumina and 29.2% for modified zeolite. The Hg0 content in flue gas reduced considerably after sorbent injection, and decreased from 40% to 22% when the sorbent injection rate was 0.22 g·m-3. Non-carbon sorbent injection combined with WFGD system could be an effective technology for controlling mercury emission of coal-fired power plant.
    Interfacially polymerized composite membranes containing propylene oxide groups for CO2 separation
    HE Wenjuan, WANG Zhi, LI Wen, LI Shichun, WANG Jixiao
    2014, 65(11):  4420-4429.  doi:10.3969/j.issn.0438-1157.2014.11.029
    Abstract ( 383 )   PDF (1986KB) ( 315 )  
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    Membranes containing polyether segments may exhibit high CO2/N2 separation performance due to strong affinity between polyether segments and CO2. Membranes with ethylene oxide (EO) groups are widely investigated, but high crystallinity of membranes with EO groups reduces gas permeance of membranes. Compared with EO group, propylene oxide (PO) group possesses an additional side methyl group that prevents crystallization and increases free volume of the membrane, which promotes gas permeance of the membrane. However, preparation of the composite membrane containing PO groups is rarely reported. In this work, composite membranes containing PO groups were prepared by interfacial polymerization with trimesoyl chloride and polyetheramines containing PO groups. The effects of PO group content and degree of cross-linking on separation performance of the membrane were investigated by using D400, D230 or T403 as the monomer in the aqueous phase. The membrane prepared with D400 exhibited the highest CO2 permeance and CO2/N2 selectivity due to its high PO group content and low degree of cross-linking. Moreover, the effects of monomer concentration, acid acceptor, and pH of the aqueous phase on separation performance of the membranes were also investigated. The high-performance membrane containing PO groups was prepared by optimizing the preparation conditions.
    Crystallization kinetics of FeSO4·7H2O in black titanium solution
    WANG Xing, SONG Xingfu, XU Yanxia, SUN Yuzhu, YU Jianguo
    2014, 65(11):  4430-4436.  doi:10.3969/j.issn.0438-1157.2014.11.030
    Abstract ( 387 )   PDF (569KB) ( 337 )  
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    The solubility of FeSO4·7H2O in black titanium solution is studied using balance method and the crystallization metastable zone is measured with FBRM online monitoring. The crystallization kinetics of FeSO4·7H2O is investigated with the method of moments through batch cooling crystallization experiments based on the population balance equation. Nucleation rate equation and growth rate equation are obtained by regressing the experimental data with the multiple linear least square method. The key parameters of the crystal size distribution are associated with stirring rate and solution temperature, which can be used to predict and control the crystal size distribution in industrial crystallization process. According to the crystallization kinetics of FeSO4·7H2O, cooling rate and stirring rate have a great effect on crystal size. Cooling crystallization process is carried out under the optimized operating conditions. The results show that the particle size of FeSO4·7H2O increases significantly and small particles reduces greatly, compared to the original process.
    Effect of pulsed electric field strength and frequency on dehydration of emulsion
    CHEN Qingguo, LIANG Wen, SONG Chunhui, LIU Zeng, ZHAO Zhongshan, WEI Xinlao
    2014, 65(11):  4437-4443.  doi:10.3969/j.issn.0438-1157.2014.11.031
    Abstract ( 461 )   PDF (1614KB) ( 255 )  
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    In order to improve the efficiency of oil dehydration and maintain the stability of dehydration electric field to satisfy the technical requirements of compactness and efficiency on onshore and offshore oil processing platform, effects of pulsed electric field strength and frequency on the emulsion dehydration are studied. The relationship between water droplet deformation and electric field strength is derived based on the telescopic model and force balance of water droplet. The expression of applied electric field frequency is obtained based on the vibration kinetic model and force balance with water droplet vibration, so that the optimal dehydration electric field frequency can be determined theoretically. The results show that there exist optimal dehydration electric field strength and frequency during electric dehydration of emulsion. The dehydration rate first increases with the external electric field, and then declines when the external electric field exceeds the critical breakdown strength, with the dehydration electric unstable. When the external electric field frequency reaches the resonance frequency of water droplet, the amplitude of water droplet is the maximum and the dehydration effect is the best.
    Separation of phenol through polyvinyl-chloride inclusion membrane with bis(2-ethyl hexyl)-phosphoric acid as carrier
    MENG Xiaorong, GAO Chenguang, WANG Lei, WANG Xudong, MA Yuan, CHEN Henan
    2014, 65(11):  4444-4450.  doi:10.3969/j.issn.0438-1157.2014.11.032
    Abstract ( 375 )   PDF (2049KB) ( 303 )  
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    A polymer inclusion membrane (PIM) system containing polyvinyl chloride (PVC) polymer matrix and bis(2-ethyl hexyl)-phosphoric acid (D2EHPA, P204), as a specific carrier, was prepared without using any additional plasticizers, expressed as PD-PIM. The chemical composition, crystallization behavior and morphology of as-prepared PD-PIM were characterized with Fourier transform infrared spectrophotometry, X-ray diffraction and atomic force microscopy. The facilitated transport of phenol through the PD-PIM was investigated. The influences of carrier content of PD-PIM, phenol concentration, pH in source phase, and HCl concentration in receiving phase on the transport were investigated. The transport kinetics of phenol and the stability of membranes were studied. The results show that the early transmission process of phenol is in line with the first order kinetic equation and the optimal transport process can be obtained with the membrane containing 70%D2EHPA/30%PVC (mass), from the source solution of phenol concentration at 400 mg·L-1 and pH 6.0, by using 0.1 mol·L-1 HCl as receiving phase. In addition, the experiments demonstrate that PD-PIM presents good stability and the phenol transport through the membrane is facilitated by co-transport.
    Modeling and steady-state multiplicity analysis of gas-phase polypropylene horizontal stirred bed reactor
    LIU Zhubin, QIU Tong, ZHAO Jinsong
    2014, 65(11):  4451-4458.  doi:10.3969/j.issn.0438-1157.2014.11.033
    Abstract ( 363 )   PDF (919KB) ( 441 )  
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    The strongly exothermic polymerization process is a nonlinear process which generally have multi-stable phenomenon. Different steady state has different local stability. The Innovene process which uses gas-phase horizontal stirred bed reactor, is one of the most advanced technology for propylene polymerization. A reactor model using Polymer Plus was built. This model is more consistent with actual cases and suitable for steady-state multiplicity analysis. The reaction parameters were obtained by fitting the GPC data of products. The steady-state multiplicity characteristics by the sensitivity analysis of steady-state model were also analyzed. An inferential analysis method for judging the stability of steady-state solutions was proposed, and the intrinsically safe operating range for each reactor area was identified finally. This is an important work for the stable operation and the development of new grades of polypropylene.
    Analysis and improvement of process industrial alarm systems traditional assessment methods
    ZANG Hao, LI Hongguang, YANG Fan, HUANG Dexian
    2014, 65(11):  4459-4464.  doi:10.3969/j.issn.0438-1157.2014.11.034
    Abstract ( 368 )   PDF (386KB) ( 361 )  
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    Alarm systems as the primary means for improving safety performances and maintaining reliable operations for industrial processes have been playing a significant role in practice. However, there exist many problems in practical applications with conventional alarm systems. Industrial accidents may occur because operators cannot handle abnormal events due to inefficient alarm systems. Motivated by these observations, this article discusses assessment of alarm systems in the management lifecycle. The paper conducts a detailed analysis for the common problems, causes and possible consequences of current industrial process alarm systems, as well as constructing an evaluation framework of alarm systems reasonable and efficient combined alarm system characteristics and parameters. Based on this framework, a quantitative assessment method is introduced, which can enjoy some advantages such as accessing data easily, implementing conveniently, and facilitating understanding for operators and managers.
    Optimization of ethyl acetate process conditions for sodium bisulfate fluidized catalytic distillation using response surface methodology
    XIAO Wu, LI Mingyue, RUAN Xuehua, HE Gaohong, DU Jian
    2014, 65(11):  4465-4471.  doi:10.3969/j.issn.0438-1157.2014.11.035
    Abstract ( 360 )   PDF (2422KB) ( 328 )  
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    A novel fluidized catalytic distillation process was developed to produce ethyl acetate based on sodium bisulfate catalyst, and response surface method was used to optimize process parameters. Firstly, single factor sensitivity analysis of five parameters, such as catalyst amount, reflux ratio, bottom heating power, acid alcohol molar feed ratio, feed rate, were carried out, and three key parameters (reflux ratio, acid alcohol molar feed ratio and feed rate) and their optimum ranges were determined. Depending on the results of single factor experiments and hydraulic limit of distillation equipment, reboiler duty of column 68 W and the amount of catalyst 2.0%(mass) acetic acid were fixed. Then central composite design methodology was used to design the experimental cases. The correlation model between three key parameters and the conversion rate of ethanol was obtained by response surface methodology based on the experimental results. By the analysis of variance and parallel experiments, the model was proved to be accurate and available. Finally, the optimum conditions were found to be feed flow of acetic acid 3.2 mol·h-1 and mole ratio of acetic acid/ethanol 3.1, reflux ratio 3.3. Under the conditions, the conversion rate of ethanol is 88.67%. Compared to the optimization parameters by a single factor sensitivity analysis process, the conversion rate of ethanol is increased by 1.0%.
    Chemical process fault detection technology based on process simulation
    LI Xiuxi, YUAN Yanjiang
    2014, 65(11):  4472-4476.  doi:10.3969/j.issn.0438-1157.2014.11.036
    Abstract ( 302 )   PDF (583KB) ( 292 )  
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    A chemical process monitoring method using Simulink Toolbox of MATLAB to invoke Aspen Dynamics to dynamically simulate the chemical process was proposed. In most of the previous literatures about model-based fault detection, the mechanistic model should be built by hand, which is very time-consuming and requires the user to have a high professional quality. Using this method can build dynamics simulation for chemical in a quick and accurate way using Aspen Dynamics even the people who don't have high professional quality in chemical engineering, meanwhile, the data collected from the factory often require correction, using Simulink Toolbox can conveniently correct the model data and measured data, at the same time the real-time factory data was collected as input data for dynamics simulation in order to achieve real-time process monitoring. The method was tested using a virtual distillation process in Aspen Dynamics, the results show that it can detect faults in chemical process with and without production change. Because the fault data also comes from a distillation process using Aspen Dynamics, the simulate data and the measured data without process fault are very similar, the method to correct the simulation data was not include.
    Performance diagnosis of MPC control loop based on weighted L2-Hausdorff subspace distance
    SHANG Linyuan, TIAN Xuemin
    2014, 65(11):  4477-4483.  doi:10.3969/j.issn.0438-1157.2014.11.037
    Abstract ( 457 )   PDF (655KB) ( 350 )  
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    In the view of the problem that the current performance evaluation method of MPC control loop cannot accurately locate the source causing performance degradation. A performance diagnosis method for control loop is proposed based on weighted L2-Hausdorff subspace distance. The method characterizes the loop performance features under different poor operating conditions by using deteriorating performance subspace, and monitors the control loop performance in real time through the model prediction residual based closed-loop potential index. When the performance degradation is detected, weighted L2-Hausdorff subspace distance is constructed to measure the similarity between the current loop performance pattern and the known ones, and the source causing performance degradation is then positioned by distance clustering. Finally, the simulation experiment on the continuous stirred tank heater(CSTH) validates the effectiveness and reliability of the proposed method.
    Simultaneous optimization of areas and cleaning schedule for heat exchanger networks
    FAN Jie, LI Jilong, LIU Linlin, ZHUANG Yu, DU Jian
    2014, 65(11):  4484-4489.  doi:10.3969/j.issn.0438-1157.2014.11.038
    Abstract ( 313 )   PDF (474KB) ( 202 )  
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    Fouling over the heat transfer surface of equipments always causes reduction to the overall heat transfer coefficient. Regular cleanings become an important means of saving energy. In the existing researches about the optimal cleaning schedule in heat exchanger networks, too many binary variables were involved, which raised the difficulties to solve the problem. This paper took the maximum allowable fouling resistance of the heat unit as the optimization variable, instead of the binary variables to represent requirement of cleaning the heat exchangers. The proposed method converted the mixed integer nonlinear programming (MINLP) problem into a nonlinear programming (NLP) problem, effectively reducing the size of the problem and the difficulty to solve the problem. With consideration of both design and operation problems of the heat exchanger network, genetic/simulated annealing algorithm (GA/SA) was adopted to optimize areas and cleaning schedule of the heat exchangers simultaneously. An example was studied to illustrate the effectiveness of the method.
    Automatic wall thickness conversion algorithm of pipeline ultrasonic inner inspection
    TANG Jian, JIAO Xiangdong, DAI Bo
    2014, 65(11):  4490-4496.  doi:10.3969/j.issn.0438-1157.2014.11.039
    Abstract ( 357 )   PDF (685KB) ( 262 )  
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    Because the pulse repetition frequency of pipeline ultrasonic inner inspection is very high, the echo data amount generated is very large, automatic acquisition of wall thickness information is the core problem. At the same time, the working condition of the actual pipeline is very complex, the useful echo signal is mixed with varied noise and uncertain disturbance, which requires the automatic wall thickness conversion algorithm with a strong adaptability. But the accuracy of second-order statistics method commonly used for the automatic wall thickness conversion is lower, the misdiagnosis rate and the miss rate is higher, and so on. Aiming at this problem, the echo signal was processed using 1.5-dimension spectrum of higher-order statistics. And according to the frequency range of wall thickness and the periodic characteristics of spectral lines, the spectrum data were intercepted and transformed again, and the improved 1.5-dimension spectrum was obtained. The transit time of the wall thickness was acquired, and then the wall thickness was obtained. Experimental results show that the inspection precision of the algorithm is very high and much better than the second-order statistics method, which is suitable for the corrosion inner inspection on long-distance oil pipeline.
    Dynamic soft sensor method based on joint mutual information
    RUAN Hongmei, TIAN Xuemin, WANG Ping
    2014, 65(11):  4497-4502.  doi:10.3969/j.issn.0438-1157.2014.11.040
    Abstract ( 297 )   PDF (632KB) ( 266 )  
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    In order to deal with time delay characteristic as well as dynamic characteristic widely exist in industrial process systems, this paper puts forward a dynamic soft sensor method based on joint mutual information. In the proposed method, maximizing the joint mutual information is taken as the criterion for selecting the continuous sub-variable set from each auxiliary variable's historical input data matrix. The selected sub-variable set forms a new data set containing the process's time delay information and dynamic information, which can be used to determine the time delay and historical data length of each auxiliary variable. The determination of the parameters of each auxiliary variable involves only the process's historical data and thus is independent of the following establishment of soft sensor model. As a result, the algorithm for constructing dynamic soft sensor models can be freely chosen according to the nonlinear degree of the specific application. The proposed soft sensor is applied to real-life debutanizer column process and its effectiveness is verified by the simulation results.
    System fault detection based on data-driven and complex networks theory
    CHEN Yu, HAN Yongming, WANG Zun, GENG Zhiqiang
    2014, 65(11):  4503-4508.  doi:10.3969/j.issn.0438-1157.2014.11.041
    Abstract ( 326 )   PDF (628KB) ( 348 )  
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    Since system structures are more and more complex, it's hard to detect the faults only through physical and chemical mechanism model. In order to overcome these difficulties, a new method based on data-driven and complex network theory is proposed using partial correlation coefficient to determine adjacency matrix of variables, then define the network model. Based on the network topology structure, the characteristics of complex system network are calculated. According to the changing of parameters of network, it can be determined whether a system has failure by contrasting the diffidence between the fault model and normal model. At last, the proposed method is applied to TE process to test its validity.
    Steam power system optimization design based on stochastic programming with recourse
    GAI Limei, SUN Li, LIU Chang, HE Gaohong
    2014, 65(11):  4509-4516.  doi:10.3969/j.issn.0438-1157.2014.11.042
    Abstract ( 333 )   PDF (481KB) ( 300 )  
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    Steam power system optimization design under uncertainty provides schedule plans in the design stage to avoid a conservative design based on deterministic design. The characteristics of uncertainties and their influence on optimization objectives and constraints were analyzed in this work. Uncertain factors were divided into two types. Fluctuations of some variables were expressed by time, and fluctuations of the others were expressed by probabilities. The first type variables caused the design to be a multi-period problem. Fluctuation of the second type variables were compensated based on stochastic programming to deal with constraint violations. A mixed integer linear programming model (MILP) based on multi-cycle stochastic programming with recourse was formulated to obtain optimal system configuration and operating state. Schedule plans were addressed in the design stage to satisfy uncertain steam and power demand.
    Online detection and control of ethylene column abnormal condition
    LUO Xionglin, ZHAO Xiaoying, WU Bo, SUN Lin
    2014, 65(11):  4517-4523.  doi:10.3969/j.issn.0438-1157.2014.11.043
    Abstract ( 416 )   PDF (626KB) ( 294 )  
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    The ethylene column is a kind of separation devices used in the petro-chemical process. It is easy for the column to enter abnormal condition because of improper operation in the distillation process. The outlet temperature will decrease with reflux increasing in normal condition and the model gain is negative. However, if reflux continues to increase, plate efficiency will decrease then outlet temperature begins to rise and model gain becomes positive then the distillation comes into abnormal condition. A kind of model gain online identification method based on the least square method for ethylene column was proposed in this paper. The symbol of model gain was identified online and then if the ethylene distillation column enters abnormal condition could be determined according to identification of model gain. Normal and abnormal control systems of the ethylene column were established and the control effect of the column controller could be determined according to the identification result of model gain, making reflux and outlet temperature controlled in the permitted range of normal condition. It could guarantee the ethylene column to work under normal condition and achieve the control of ethylene column under normal and abnormal condition.
    Electrodeposition of Ni-Mo alloy from deep eutectic solvents and its catalytic properties for hydrogen generation
    WANG Hongzhi, HUANG Bo, ZHANG Weiguo, LIU Xiangting, YAO Suwei
    2014, 65(11):  4524-4529.  doi:10.3969/j.issn.0438-1157.2014.11.044
    Abstract ( 517 )   PDF (3572KB) ( 355 )  
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    Ni-Mo alloys were electrodeposited in the deep eutectic solvent system. To obtain the information on deposit's morphology, structure and hydrogen evolution activity, scanning electron microscopy (SEM), X-ray diffraction (XRD) and polarization curve test were used respectively. SEM images and XRD pattern showed that the prepared alloy had a nanocrystalline structure with average crystallites size of 2.2 nm. The deposit contained about 5% (mass) Mo and had a large roughness factor. Polarization curves indicated that hydrogen generation potential of Ni-Mo alloy deposited in ionic liquid had a positively shift of about 100 mV compared to Ni-Mo alloy deposited in aqueous solution and had a positive shift of about 250 mV compared to pure Ni electrode at current density of 0.1 A·cm2.
    Anti-coking property of Cr/W/rare earth oxides coating for transfer line exchanger
    LU Yang, LIU Jinglei, XU Hong, QU Xiaoyu, LIU Jianshu, WAN Shun
    2014, 65(11):  4530-4535.  doi:10.3969/j.issn.0438-1157.2014.11.045
    Abstract ( 356 )   PDF (6305KB) ( 313 )  
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    Transfer line exchanger (TLE) is an important equipment for ethylene cracking unit. In actual operation, coke formation occurs on the inner surface of tubes in TLE. In effectively inhibit coking on the inner surface of tubes, inert coating of Cr/W/REO was applied on the surface of the tube metal. With aids of ethylene cracking simulator, metallurgic microscope, electronic scanning microscope (SEM), and transmission electron microscopy (TEM), coking inhibition performance of inert coating was studied, including the characteristics of coke surface and coking amounts of specimens. Serious coking occurred on the blank specimen surface with catalytic coke and granular coke, while the coated specimen showed great anti-coking effect without catalytic coke and the coke layer was easy to remove. Coking inhibition rate reached 79.1%.
    Structural parameter optimization of spiral groove dry gas seal under low or medium pressure
    PENG Xudong, JIANG Jinbo, BAI Shaoxian, LI Jiyun, WANG Yuming
    2014, 65(11):  4536-4542.  doi:10.3969/j.issn.0438-1157.2014.11.046
    Abstract ( 301 )   PDF (824KB) ( 216 )  
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    Based on full factorial design, optimization of structural parameters of a spiral groove dry gas seal (S-DGS) under low or medium pressure was performed. Based on the theory of gas lubrication, the sealing characteristic parameters, such as increase ratio of hydrodynamic open force, film stiffness and film stiffness to leakage ratio of an S-DGS under low or medium pressure were analyzed, and the preferred value ranges of structural parameters of spiral grooves were obtained. The concept of characteristic parameter optimization zone of an S-DGS was presented. The optimum sealing performance with different compressibility numbers of an S-DGS could be properly reflected by characteristic parameter optimization zone. When an S-DGS was operated under low or medium pressure and at high-speed, excellent sealing performance could be obtained for an S-DGS when spiral angle was between 10° and 25° and groove depth was between 5 mm and 10 mm. Excellent hydrodynamic effect and axis film stability could be obtained when groove-to-dam ratio was between 1.5 and 4.0 and groove length-width ratio was between 2 to 8. Excellent comprehensive sealing performance could be obtained when groove-to-dam ratio was between 0.7 and 1.5, groove length-width ratio was between 2 to 5.
    Fractal model of temperature distribution of frictional interface in contacting mechanical seals
    DING Xuexing, YAN Ruqi, CHEN Jinlin, ZHAI Xiao
    2014, 65(11):  4543-4550.  doi:10.3969/j.issn.0438-1157.2014.11.047
    Abstract ( 438 )   PDF (1320KB) ( 330 )  
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    In order to reveal the temperature distribution of the frictional interface mechanical seals, the end face morphology of mechanical seals was characterized by fractal parameters. According to re-established contact deformation model of the micro-convex body, the fractal model of the maximum temperature and the temperature distribution of mechanical seals were established by heat exchange and probability theory. With numerical methods its maximum temperature, temperature distribution and influence factors were analyzed. The highest temperature of frictional interfaces increased linearly with increasing rotating speed when fractal dimension was constant. But the highest temperature of frictional interfaces decreased nonlinearly with increasing fractal dimension when rotating speed was constant. Dimensionless maximum contact temperature also increased as dimensionless characteristic scale was larger. When lubricant film vaporization temperature was known, the real contact area of the non-normal lubrication part could be calculated by using the temperature distribution density function, providing foundation for further research on wear and heat damage and had great significance both in operating and design of contacting mechanical seals.
    Partial load performance of biogas engine driven air source heat pump system
    WU Jiying, MA Yimin
    2014, 65(11):  4551-4556.  doi:10.3969/j.issn.0438-1157.2014.11.048
    Abstract ( 407 )   PDF (955KB) ( 333 )  
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    A biogas engine driven heat pump system for comprehensive utilization and conservation of energy is presented. An experimental platform was constructed and the system performance was tested. Based on theoretical analysis and experimental data, the relationship between load rate of biogas engine and biogas consumption, waste heat recovery, system coefficient of performance (COP) and primary energy ratio (PER) was studied. Results indicate that the partial load performance of this system is good, with the maximum COP of 4.18 and the maximum PER of 1.4 for recovering the waste heat of biogas engine exhaust fume only. Therefore, the biogas engine driven air source heat pump system can significantly improve heating capacity and lower energy consumption so as to achieve comprehensive and effective utilization of biogas energy.
    Evaluation of instant catapult steam explosion combined with chemical pretreatments on corn stalk by components and enzymatic hydrolysis analysis
    LIU Liyang, HAO Xuemi, LIU Chenguang, BAI Fengwu
    2014, 65(11):  4557-4563.  doi:10.3969/j.issn.0438-1157.2014.11.049
    Abstract ( 426 )   PDF (2614KB) ( 279 )  
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    Combining with instant catapult steam explosion (ICSE), corn stalk was pretreated by different chemical methods, including dilute acid, sodium hydroxide, aqueous ammonia, organic solvent, and ionic liquid. In order to obtain a green and highly efficient process, materials were analyzed by components and enzymatic hydrolysis analysis. ICSE could significantly prompt the effects of chemical methods on lignocellulose pretreatment. Among these approaches, ICSE combined with sodium hydroxide had the highest glucose yield 77.54%. Meanwhile, compared with the solo ionic liquid pretreated method, ICSE combined with ionic liquid pretreatment increased glucose yield by 7.78 folds, reaching 60.04%. Considering the requirements of efficiency, green process and low energy cost on pretreatment, the method of ICSE plus ionic liquid was selected as the optimal method and materials then were analyzed with Fourier transformed infrared (FT-IR), X-ray diffraction (XRD) and scanning electron microscope (SEM) to analyze its mechanism. The materials treated by ICSE were porous, unconsolidated, low hemicellulose content and inclined to be dissolved by ionic liquid. When ICSE was combined with ionic liquid pretreatment, lignocellulosic cellulose components were transformed from cellulose-Ⅰ to cellulose-Ⅱ with the lowest crystallinity index.
    Influence of steam on NO formation during oxy-coal combustion
    HU Xiaowei, WU Wangchen, YAO Hong
    2014, 65(11):  4564-4570.  doi:10.3969/j.issn.0438-1157.2014.11.050
    Abstract ( 330 )   PDF (560KB) ( 253 )  
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    The influence of H2O on NO formation during oxy-coal combustion was investigated in a drop-tube furnace. A bituminous coal was selected and burnt at temperature of 1273 K under O2/N2, O2/CO2 and O2/CO2/H2O atmospheres, respectively. At different O2 contents 5%, 21%, and 30%, the samples were analyzed for increasing residence time from 0.2 s to 1.1 s. The results show that NO formation is suppressed by addition of H2O. The mechanism of NO reduction is due to the change of volatile-N chemistry with H2O addition. The H2O influence on homogeneous NO formation goes up with the increase of O2 concentration.
    Influence of crude oil composition on wax deposition on tubing wall
    LI Chuanxian, BAI Fan, WANG Yan
    2014, 65(11):  4571-4578.  doi:10.3969/j.issn.0438-1157.2014.11.051
    Abstract ( 603 )   PDF (678KB) ( 474 )  
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    The wax deposition was studied for man-made crude oil with various compositions (different contents of resin, asphaltene and wax) under various conditions in a rotary wax deposition facility. The influence of the compositions was explored by sediment sampling from tubing wall, analyzing with the differential scanning calorimetry (DSC) and using four components method. Combined with mechanism of the wax deposition initiated by resin and asphaltene, it was found that lower content resin and asphaltene in crude oil could have a synergistic effect with paraffin molecules on the wax deposition, while for higher content resin and asphaltene they were attached to the pipe wall in the form of paste, although the existence of resin and asphaltene could weaken the driving force for paraffin molecule migration and impede deposition of paraffin molecules. The results obtained from studying on the effect of various wax contents on wax deposition showed that higher average carbon number of paraffin molecules in man-made crude oil was, less content of wax in the wax layer deposited. But the paraffin molecules with more carbon number could take place eutectic roles with resin and asphaltene easily, due to they were of longer carbon chain, leading to they was easier to deposit on the pipe wall with resin and asphaltene together.
    Photolysis of dimethyl sulfide by microwave electrodeless discharge lamp
    ZHANG Tingting, QI Lei, YU Yang, YU Jiang
    2014, 65(11):  4579-4585.  doi:10.3969/j.issn.0438-1157.2014.11.052
    Abstract ( 390 )   PDF (670KB) ( 252 )  
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    Photolysis of dimethyl sulfide (DMS) by microwave electrodeless discharge lamp (MEDL) was conducted in this study. Removal efficiency decreased with increasing inlet concentration of DMS, but could be increased to 94.3% while residence time of DMS in the photo-reactor was kept at 10 s. Direct photolysis and indirect photo-oxidation by excited states of atomic oxygen O(1D) and radical·OH were regarded as the contribution to DMS degradation in MEDL, especially, O(1D) played the key role of oxidative species in mineralizing DMS to inorganic chemicals, such as SO42-, CO2 and H2O.
    SO2 removal from simulated smelting gas with (NH4)2S and sulfur recycling
    WANG Langlang, WANG Xueqian, NING Ping, SHI Yong, MA Yixing, JIA Rui, WANG Fei
    2014, 65(11):  4586-4592.  doi:10.3969/j.issn.0438-1157.2014.11.053
    Abstract ( 522 )   PDF (617KB) ( 417 )  
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    SO2 in simulated smelting gas was absorbed by (NH4)2S solution, to obtain a mixed solution of (NH4)2S2O3 and NH4HSO3. After that the mixed solution was transferred into a special high pressure reaction kettle, and sulfur and ammonium sulfate were generated through the REDOX reaction under controlled conditions. The influence of SO2 absorption process condition and REDOX process condition were investigated. Under the condition of pH=3—7, SO2 flow velocity of 300 ml·min-1, normal temperature, (NH4)2S solution concentration of 0.2—1.2 mol·L-1, absorption efficiency of SO2 reached more than 99.8% and H2S was not produced. Under the condition of pH=2.5—3.0, reaction temperature 130℃, sulfur recovery rate could reach more than 95% after one hour of reaction. Ammonium sulfate could be obtained through evaporation crystallization. Sulfur and ammonium sulfate generated during reaction were characterized by X-ray diffraction (XRD) and X-ray fluorescence (XRF). Purity of sulfur was 99.14% and percentage of nitrogen in ammonium sulfate was 23.6%.
    Dioxins emission control from hazardous waste incinerator by SO2 recycling inhibition
    WU Hailong, LIN Xiaoqing, YAN Mi, CHEN Tong, LU Shengyong, LI Xiaodong, YAN Jianhua
    2014, 65(11):  4593-4598.  doi:10.3969/j.issn.0438-1157.2014.11.054
    Abstract ( 435 )   PDF (528KB) ( 271 )  
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    Sulfur acts as an effective inhibitor of dioxins formation, and such action has been proved in laboratory studies, but few studies in actual waste incinerators are reported. To control the emission of dioxins from hazardous waste incinerator (HWI) effectively, a new pilot scale system with SO2 recycling and fly ash thermal treatment from the bypass flue gas in an actual HWI (50 t·d-1) was developed. An absorbent was used to realize SO2 recycling by which SO2 absorption was conducted by the absorbent in the flue gas and SO2 desorption was conducted in the low-temperature thermal treatment system. The capacity of SO2 accumulation and inhibition of dioxins synthesis of the system was studied, and it was found that the system could operate continuously. The system could maintain a high SO2 concentration of 100 mg·m-3 after adding a certain amount of other S-compounds and reduce more than 80% of dioxins emission factor. Therefore, the SO2 recycling inhibition technology provides guidance for dioxin emission reduction during waste treatment, and the long-term stable operation of the system will play a key role in achieving low emission of dioxins, but some relevant parameters of the pilot system still need further optimization.
    Waterborne polyurethane adhesive modified by epoxy oil soybean and 3-aminopropyltriethoxysilane
    HE Feiqiang, FU Heqing, ZHOU Wei
    2014, 65(11):  4599-4606.  doi:10.3969/j.issn.0438-1157.2014.11.055
    Abstract ( 420 )   PDF (3406KB) ( 499 )  
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    Waterborne polyurethane (WPU) modified by epoxy soybean oil (ESO) and 3-aminopropyltriethoxysilane (KH550) were synthesized. The properties of the modified WPU were characterized by FTIR, TG, DSC, DMA, AFM, particle size analyzer and tensile test machine. The effects of contents of ESO and KH550 on the properties of WPU emulsion, its film and adhesive strength were studied. And the effect of KH550 on the crystallinity and microphase separation of WPU was analyzed. With the increase of contents of ESO and KH550, the properties of WPU dispersion were improved, the water absorption of WPU film decreased first, and then increased. Tensile strength increased, while elongation at break decreased. The T-peel strength of the adhesive to PVC/PVC increased first, and then decreased. With increasing KH550 content, thermal stability of the WPU film was improved, crystallinity decreased, degree of mixing of soft segment phase and hard segment phase was enhanced. When the contents of ESO and KH550 were 4% and 2%(mass), respectively, the properties of WPU adhesive were perfect.
    Synthesis, characterization and curing characteristics of double benzoxazine contained double DOPO based on bisphenol A
    LIU Jianhua, SHI Tiejun
    2014, 65(11):  4607-4613.  doi:10.3969/j.issn.0438-1157.2014.11.056
    Abstract ( 1006 )   PDF (850KB) ( 626 )  
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    The bisphenol A contained double DOPO (2DO) was synthesized by using double benzoxazine based on bisphenol A(DBOZ) and DOPO. And the double benzoxazine contained double DOPO based on bisphenol A (2DD) was synthesized by using 2DO,aniline and paraformaldehyde. FT-IR, NMR were used to characterize the chemical structure of 2DO and 2DD. Curing characteristics were studied with DSC and thermostability was studied with TG. In N2 atmosphere, initial decomposition temperature of 2DD was 353℃. At the temperature of 442℃, the fastest speed of decomposition was achieved. At the temperature of 800℃, carbon residue was 40.40%. Mass-change rate at the temperature of 300℃ was 3.97%. Compared with double benzoxazine based on bisphenol A,initial decomposition temperature increased by nearly 41℃,the fastest speed of decomposition increased by nearly 70℃ and carbon residue increased by nearly 3.21%.
    Structure and properties of continuously devulcanized ground tire rubber using independently designed single screw extruder
    LÜ Xiaolong, LÜ Baiyuan, HUANG Hanxiong, JIANG Qingyan
    2014, 65(11):  4614-4619.  doi:10.3969/j.issn.0438-1157.2014.11.057
    Abstract ( 534 )   PDF (2490KB) ( 440 )  
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    Using independently designed single screw extruder, ground tire rubber (GTR) powder was devulcanized continuously to prepare devulcanized ground tire rubber (DGTR). The DGTR was further revulcanized to prepare revulcanized DGTR samples. The gel fractions of the DGTR and the crosslink densities of the revulcanized DGTR samples decreased and the tensile strengths and elogations at break of the revulcanized DGTR samples increased gradually with increasing screw speed. The best devulcanization effectiveness was achieved under 40 r·min-1 screw speed and 205℃ devulcanization temperature. The revulcanized DGTR sample prepared under this condition exhibited tensile strength and elogation at break of about 11 MPa and 386% respectively. Inferring from the Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses, parts of S—S and C—S bonds in the GTR powder were broken under both shearing and heating in the independently designed single screw extruder.
    Effect of ultraviolet aging on properties and structure of polystyrene
    YAO Peipei, LI Chen, XIAO Shengling
    2014, 65(11):  4620-4626.  doi:10.3969/j.issn.0438-1157.2014.11.058
    Abstract ( 541 )   PDF (1664KB) ( 617 )  
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    The variation of external appearance and cushioning properties of expanded polystyrene (EPS) was investigated and the change in internal structure of EPS was analyzed by using the ultraviolet (UV) accelerated aging method. The physical properties and chemical structure of EPS before and after aging were determined by colorimetric analysis, mechanical properties test, gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR/FTIR). With increasing time of UV accelerated aging, on the molecular chain of EPS some coloring groups that turned the color of the sample surface yellow were produced. With increasing aging time, minimum cushioning coefficient value increased, and cushioning efficiency decreased. When aging time was more than 100 h, growth rate of cushioning coefficient had a significant rise, and there was a tendency to lose cushioning property. With increasing aging time, molecular weight of EPS decreased, and molecular weight distribution increased from 2.13 to 3.76, indicating photo-oxidative degradation. So stability of molecular structure of EPS was destroyed. C element content decreased and O element content increased gradually in molecular structure of EPS. UV irradiation excited EPS surface, and oxidation occurred under the interaction of water and temperature to generate new functional groups, such as C O, C—OH bonds. Accelerated aging broke macromolecular chain to reorganize chemical bond in EPS structure, resulting in the decline of mechanical properties. The aging behavior of EPS is the fundamental basis to determine service life and service environment. It provides a reference for the reasonable application of EPS liner in transport packaging processes.
    Preparation and sustained release properties of acidified-attapulgite/alginate composite material
    WU Jie, DING Shijie, CHEN Jing, JIANG Jinlong, WANG Junjun
    2014, 65(11):  4627-4632.  doi:10.3969/j.issn.0438-1157.2014.11.059
    Abstract ( 322 )   PDF (3506KB) ( 247 )  
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    A composite material with improved sustained release properties, based on hybridization of sodium alginate (SA) and acidified-attapulgite (H+-ATP), was prepared by solution mixing and was developed for drug carrier. Diclofenac sodium (DS) was selected as the model drug to obtain release data from the composite-based matrix tablets in phosphate buffer solution (PBS) in vitro. The morphology and structure of the composite were characterized by FTIR, SEM and XRD. The effect of content of acid modifier, H+-ATP content and mixing time on the slow release properties of the composite were investigated to obtain optimum process condition. The composite with 60% H+-ATP treated by 12 mol·L-1 HCl exhibited perfect release properties. Compared with pure alginate tablets, the burst release of 42.6 % in 2 h decreased to 23.7% for the prepared composite. The drug release process of the composite was better fitted by the Ritger-Peppas model and the rate of drug release was governed by both diffusion and swelling mode. The introduced H+-ATP improved the release properties of alginate significantly.
    Leak detection and location for natural gas pipelines based on acoustic waves
    LIU Cuiwei, LI Xuejie, LI Yuxing, LIU Guangxiao, QIAN Haocheng, CAO Pengfei
    2014, 65(11):  4633-4642.  doi:10.3969/j.issn.0438-1157.2014.11.060
    Abstract ( 778 )   PDF (3038KB) ( 634 )  
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    In order to study the principle and technologies of acoustic leak detection for natural gas pipelines, an acoustic method is applied. A simulation model is established based on the field conditions to analyze and verify the generation mechanism of leakage acoustics. The field experiments are carried out based on the simulation results and measured signals are processed by joint time-frequency analyses including short time Fourier transform, wavelet transform, Hilbert-Huang transform and Generalized S transform to extract the characteristics that propagate a long distance. The characteristics are applied to detect the leak of long distance pipeline with satisfactory results. Finally the characteristics are used to locate leakages. The results show that the characteristics extracted by signal-processing from leakage acoustic signals can be applied to leak detection for long-distance natural gas pipelines.