CIESC Journal

Overview on subspace model identification methods

LI Youfeng;SU Hongye;CHU Jian

2006, 57(3): 473-479.

Abstract ( 744 )

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As a useful complement to the classical linear system identification methods,the subspace model identification (SMI) methods have drawn much research attention recently.Based on input-output data, state space models are directly identified by the SMI methods combined with the system theory,linear algebra and statistics.In this paper, basic idea of SMI methods is presented at first.Then three basic algorithms, i.e., N4SID, MOESP and CVA, are discussed in terms of difference and similarity, implementation, statistical features and model stability.Some other SMI methods are subsequently reviewed such as the SMI methods for continuous time systems, the frequency domain SMI methods,the closed-loop SMI methods and SMI methods for nonlinear systems.In order to demonstrate the features of SMI methods, comparison between the SMI methods and the prediction error methods(PEM) is made based on the same data sets collected from real-life application.Finally, some further theoretical problems are discussed.

Effects of solvents on crystal habit of hydroquinone

LI Xiaona;YIN Qiuxiang;CHEN Wei;WANG Jingkang;GAO Haijian

2006, 57(3): 480-485.

Abstract ( 644 )

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The effects of solvents such as water, methanol, ethanol, 1-propanol, 2-propanol and 1-butanol on the crystal habit of hydroquinone were studied.Growth experiments of hydroquinone single crystals were performed in a jacket crystallizer by cooling crystallization.Scanning electron microscopy, differential scanning calorimetry, powder X-ray diffractometry and single crystal X-ray diffractometry were used to characterize the produced crystals.The experimental results showed that the crystal habit of hydroquinone was evidently influenced by the property of solvents.The length-diameter ratio of the hydroquinone crystal decreased with the dielectric constant of solvent.Based on the theoretic prediction by Cerius² software, the mechanism of the effect of solvent on the crystal habit of hydroquinone was analyzed.

Flow distributions of header configurations in plate-fin heat exchangers with particle image velocimetry (PIV)

ZHOU Aimin;LI Yanzhong;WEN Jian;ZHANG Ke;WANG Jiang

2006, 57(3): 486-490.

Abstract ( 840 )

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Based on numerical simulation,the flow distributions of the ordinary header and three improved headers was studied with PIV, and a series of velocity streamline graphs of different cross sections were obtained.At Re＝6.22×10⁴ the outlet flow distributions of the ordinary header and an improved header, and the effects of flow distribution of three improved headers with different middle-hole-area ratios were compared.The experimental results showed that the perforated plate header configuration could effectively improve the uniformity of fluid flow distribution.Flow maldistribution parameter S_U and the ratio of the maximum velocity to the minimum velocity θ_U of the type C header configuration were minimum.There was an optimum point between flow distribution and the middle-hole-area ratio.

Modelling and numerical simulation of boiling flow of liquid nitrogen in vertical tube

LI Xiangdong;WANG Rongshun;HUANG Rongguo;SHI Yumei

2006, 57(3): 491-497.

Abstract ( 699 )

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The closure equations of the two-fluid model for heat and mass transfers between liquid phase and vapor phase during boiling flow of liquid nitrogen were developed.The formulas of the interfacial area concentration and the bubble departure diameter were modified for accurate prediction.The equations were incorporated into the two-fluid model and the commercial CFD code CFX-4.3.Two-dimensional numerical simulations of subcooled boiling flow of nitrogen in a vertical tube were performed by using the modified CFD code.The numerical results showed encouraging agreement with the experimental data available in the literature.Detailed distributions of the void fraction, heat transfer coefficient and liquid temperature difference were obtained, leading to better understanding of the basic mechanisms of boiling flow and related cooling systems.

Theoretical analysis of coaxial cylindrical featured electrodes for EHD enhancement of phase-change heat transfer

WAN Jinqing;LI Ruiyang; YU Hongling; DONG Wei;HUANG Xuan

2006, 57(3): 498-502.

Abstract ( 677 )

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Based on electrohydrodynamics(EHD)enhancement of boiling heat transfer outside a tube and condensation heat transfer inside a tube in high voltage DC electric field, three coaxial cylindrical featured electrodes were presented.These three featured electrodes had minimum electric field strength,minimum electric field force and minimum work consumption, respectively，and the latter two electrodes were derived by the authors for the first time.The geometric characteristics of the electrodes were analyzed and the results showed that the diameter of the electrode played an important role in EHD enhancement of phase-change heat transfer.

New mass transfer model of ammonia vertical falling-film absorption

NIU Xiaofeng;WANG Lianghu;DU Kai

2006, 57(3): 503-508.

Abstract ( 594 )

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On the basis of Harriott’s theory,a new mass transfer model was presented.It expanded the working point of eddy in falling-film absorption from a geometric point to an area,and divided the whole flow into a turbulent flow zone and a non-turbulent flow zone.When the flow was non-turbulent, Levich thickness was handled in different ways in wave trough zone and wave crest zone.The velocity of wave motion was amended in the turbulent flow zone.The deviation between the model and experimental data of ammonia water falling-film absorption on a smooth vertical tube was not more than 10% in the turbulent flow zone and 15% in the non-turbulent flow zone.The influences of diffusion coefficient, Levich thickness and wave period on mass transfer coefficient were expressed correlation as the relation of two non-dimensional numbers.

Exergy transfer characteristics of forced convective heat transfer through a smooth duct subjected to constant heat flux

WU Shuangying; CHEN Yan;LI Yourong;ZENG Danling

2006, 57(3): 509-514.

Abstract ( 775 )

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Based on the first and second laws of thermodynamics and the theory of non-equilibrium thermodynamics, a new systematic approach to studying the exergy transfer processes of forced convective heat transfer through a duct with constant heat flux for fully developed turbulent flow was introduced.The local and mean convective exergy transfer coefficient, exergy flux, exergy-transfer Nusselt number were defined and the equation of convective exergy transfer rate was developed and their new generalized expressions were derived.By reference to a smooth duct, the numerical results of exergy transfer characteristics were obtained,and the effects of Reynolds number, non-dimensional heat flux and different cross-sectional locations in the duct on exergy transfer process were analyzed.In addition, a comparison of the results of exergy transfer with that of energy transfer was also discussed.

Varying composition capacity control air conditioning system with ternary refrigerant mixture

CUI Xiaoyu;WU Xianzhong;LI Meiling

2006, 57(3): 515-520.

Abstract ( 717 )

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On the basis of theoretical analysis of the separation characteristic of the non-azeotropic ternary refrigerant mixtures R407C, a varying composition capacity control air conditioning system is introduced in this paper.According to the theoretical refrigeration cycle performance analysis, the adjustment performance and energy saving potential of the system were analyzed.The air conditioning system’s cycle performance using ternary refrigerant mixtures of different compositions was tested.The cooling capacity could be adjusted by varying the composition of the refrigerant mixture at the same flow rate.The energy efficiency ratio could be maintained relatively constant, saving energy when the system runs beyond the design conditions.

Mass transfer model of supercritical fluid extraction of natural products

ZHAO Yueqiang;WU Zhengming;LIU Weiwei

2006, 57(3): 521-525.

Abstract ( 830 )

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The mass transfer mechanism of extracting natural products with supercritical fluid was analyzed and the analytical solution of the dynamic model of supercritical fluid extraction was deduced through rationally simplifying the differential mass balance equations.A new dimensionless number Bz was proposed to characterize the dynamic mass transfer conditions of the process accurately, and a characteristic time t_k was found that -dr_c/dt reaches the minimum value when t=t_k, which might be the competing results of intraparticle diffusion resistance with intraparticle mass transfer driving force.The complete extraction time t_ex, cumulative extraction yield Y as a function of time t and the influence of flow rate Q on extraction yield Y were calculated with the model.The results of calculation fitted well with the experimental data of literature.This simple and reliable model could be used to predict ,analyze, design ,simulate and optimize the process of extracting natural products with supercritical fluid.

Flow boiling in microchannel with nonazeotropic mixture

MA Hugen;HU Zicheng

2006, 57(3): 526-529.

Abstract ( 662 )

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Experimental results are reported for the flow boiling heat transfer characteristics of nonazeotropic refrigerant mixture of R32 and R134a(25%/75%) in a microchannel with d=0.86 mm.The research results show that when the mass quality is greater than 0.1, the mass quality and mass flux have almost no effects on the heat transfer coefficients of flow boiling.Heat transfer coefficients of the flow boiling in the microchannel are dependent mainly on heat flux.Nucleation is dominant in the heat transfer process for most situations.The flow boiling heat transfer coefficients in microchannel are 30%—200% higher than those in normal tubes.Experimental correlation is presented with deviation of no more than 25%.

Modeling of chaotic signals based on genetic algorithms in vapor-liquid-solid boiling flow

LIU Mingyan;YANG Yang

2006, 57(3): 530-535.

Abstract ( 639 )

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Time series modeling is more difficult but more meaningful than the modeling on the average characteristics of the system.It has recently been shown that the fluctuation behavior in the system with vapor-liquid-solid boiling flow is chaotic.Hence, the time series modeling was studied in this work from the point of view of nonlinear hydrodynamics.Based on the time series data of wall temperature of heated tube in an evaporator with vapor-liquid-solid boiling flow, the genetic algorithm is used to develop global models by which the nonlinear hydrodynamic behavior of the system can be described in different operation conditions.The model equations were in the forms of iteration functions.Comparison and analysis of the data obtained from the model and those from the experiments were made.The results showed that the calculated values from the models were in good agreement with those measured in the experiments, and the hydrodynamic behavior of the vapor-liquid-solid three-phase flow system can be well described by these models.

Fluctuation characteristics of liquid slug length for slug flow in downward inclined pipeline

LUO Xiaoming;HE Limin;WANG Haiqin

2006, 57(3): 536-540.

Abstract ( 644 )

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The differential pressure signal of slug flow was gathered in a downward inclined pipe, and the time series of liquid slug length was obtained by utilizing the cross correlation analysis.The fluctuation characteristics of liquid slug length was discovered by using the statistics theory and fractal theory to analyze the time series of liquid slug length.The results showed that the effect of gas superficial velocity on liquid slug length was greater than the effect of liquid superficial velocity.When the liquid superficial velocity was relatively high, with increasing mixture velocity, the chaos of liquid slug length fluctuation would increase.When the liquid superficial velocity was relatively low, with increasing mixture velocity, the chaos of liquid slug length fluctuation would decrease.On the condition of a larger pipe inclination angle, the distribution of liquid slug lengths was more concentrated in a smaller range.The larger the inclination angle was, the better the long-range dependence of liquid slug length fluctuation was.

Similarity of gas-solid flow behaviors in fully developed region of CFB

QI Xiaobo;ZHOU Songrui;HUANG Weixing;ZHU Jingxu;SHI Yanfu

2006, 57(3): 541-547.

Abstract ( 540 )

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Similarity of upward gas-solid two-phase flow behavior in the fully developed zone under different operating conditions was further studied based on the axial pressure gradients and local solids holdups from the literature and the authors’laboratory.The results showed that the detailed hydrodynamic similitude in the fully developed zone of the CFB risers under different operating conditions could be characterized by the empirical similarity number presented in this work.It was also found that the solids holdups in the fully developed zone change linearly with the empirical similarity number.For the upward gas-solid two-phase flow systems, operating at different conditions,if the similarity numbers were the same,the local solids holdups,the solids concentrations inside cluster and the cluster existence times would display the same axial and radial distributions, respectively,in the fully developed zone.The preliminary study showed that the empirical similarity number is independent of the upward gas-solid CFB systems.

Observation of concentration boundary layer of flowing gas-liquid interface with laser holographic interferometry

YANG Zujie;GUO Ying;YUAN Xigang;ZENG Aiwu;YU Guocong

2006, 57(3): 548-552.

Abstract ( 699 )

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Laser holographic interferometer system was used to visualize the concentration profiles within the vicinity of the gas-liquid interface under the co-current flowing conditions of gas/liquid two fluids.Interferograms on different experimental conditions were obtained, and the concentration profiles as well as the thickness of the concentration boundary layer were calculated.Finally the influence of the Reynolds number of the liquid phase on the boundary layer thickness was discussed.

Generalized method for parallel computation of particle methods and its application

TANG Dexiang;GE Wei;YI Feng;WANG Xiaowei;GUO Li;REN Ying

2006, 57(3): 553-557.

Abstract ( 668 )

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Particle methods have been widely used in many fields such as chemical engineering, material science and energy.Based on an introduction to the application background and characteristics in the programming and implementation of particle methods, some key problems in designing the main computational module of a general software platform for parallel computation with partical methods are discussed.The implementation of the main module of this platform and relevant template library are introduced in the paper.Object-oriented programming and template techniques are adopted in the software development, and the codes are of good generality and extensibility.The software was tested in simulation of 3D air flow in stove hearth using the PPM method and in MD simulation of phase separation of two immiscible components in membrane.The results manifest that the platform provides good facility for large scale particle simulation.

Concentration distribution in catalytic combustion heat exchanger at cold state

WANG Sheng;WANG Shudong

2006, 57(3): 558-563.

Abstract ( 496 )

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A highly compact plate-fin catalytic combustion heat exchanger (CCHE) derived from plate-fin heat exchanger,which coupled exothermic reaction with evaporation was proposed.The configuration of plate-fin offered a high degree of compactness，minimized heat transport resistance and favored scale-up.Uniform concentration distributions contributed to further enhancement of the heat efficiency of CCHE.A porous media model was adopted to study the concentration distributions under diverse space velocities and pressure-outlet positions by using cold test and three-dimensional computational fluid dynamics(CFD) simulations.The computational and experimental results indicated that fluid flow maldistribution was significant under various GHSV.Some improvements on distributions could be achieved by changing the location of off-gas outlet.However novel distributors should be developed.Comparison of experimental measurements and simulations showed similar trends.Consequently simulations on concentration distributions in the combustion chamber provided a guidance for further improvement.

Transformation and photocatalytic activities of nano-sized TiO₂ doped by transition metal ions

ZHENG Guangtao;SHI Jianwei;CHEN Mingxia;YUAN Jian;SHANGGUAN Wenfeng

2006, 57(3): 564-570.

Abstract ( 622 )

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The TiO₂ nanoparticles doped by Mo⁶⁺, Cr³⁺ and Fe³⁺ ions with the ion concentration of 0.05%（mol） were prepared by the Sol-Gel method at calcination temperatures of 550℃ and 580℃, and characterized by XRD, BET and FT-IR.The results showed that Mo⁶⁺ ion doping efficiently inhibited the phase transformation of TiO₂ at different temperatures, while Cr³⁺ and Fe³⁺ ion doping played a reverse effect at 550℃ and 580℃ respectively, which might be caused by the disparate status of doping ion in the titania crystals due to different calcination temperatures.The photocatalytic decomposition of dye rhodamine B was utilized to evaluate the influences of calcination temperature and ion concentration on the photocatalytic activities of doped nano-sized TiO₂.It was found that the influences of ion doping on the photocatalytic activities of titania were consistent with the influences of ion doping on phase transformation.The TiO₂ doped by Mo⁶⁺ with the ion concentration of 0.05%（mol） showed the highest photocatalytic activities.

Inverse problem in gas phase homogeneous chemical reaction kinetics study using in situ Raman spectroscopy—parameter identification

HUANG Min;WU Qian;LI Dongming;Chinho Park;Tim Anderson

2006, 57(3): 571-576.

Abstract ( 1026 )

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A new scheme was proposed for investigating homogeneous gas phase chemical reaction kinetics.Direct mathematical deconvolution through inverse problem scheme was achieved by taking the advantage of the spatial resolved nature of Raman spectroscopy.Three-dimentional, spatially resolved gas phase species concentration profiles along the centerline of a cylindrical inverted vertical impinging flow reactor were obtained by in situ measuring the ratio of the vibrational Raman intensity of reactant to that of N₂.Gas phase temperature profile along the centerline was obtained simultaneously through N₂ Raman rotational spectra.Binary diffusion coefficient and homogeneous gas phase chemical reaction rate constant were then estimated through the output least square method.The stability of the inverse problem was achieved by using the Tikhonov regularization method.TMGa-N₂ binary diffusion coefficient and homogeneous decomposition reaction rate constant of TMGa in N₂were identified.The identified TMGa-N₂ binary mass diffusion coefficient and TMGa thermal decomposition rate constant are 0.08 cm²•s^-1 and 3.4×10¹⁵ exp(60.1/RT) respectively, which match literature values very well.

Aerobic oxidation of alcohols catalyzed by supported Ru/HMS zeolite

JI Hongbing;QIAN Yu;WANG Tingting;ZHANG Meiying

2006, 57(3): 577-581.

Abstract ( 581 )

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Supported Ru/HMS zeolite was prepared via the impregnation method.Characterization results showed that HMS was partially covered by ruthenium on its surface, and the degree of irregularity on the catalyst surface was increased.Thus, specific surface area and pore volume of this catalyst were also increased.The Ru/HMS catalyst exhibited efficient catalytic performance towards liquid-phase oxidation of allylic and benzylic alcohols under mild conditions in the presence of molecular oxygen.

A kinetic model of Rhubarb anthraquinones extraction by supercritical CO₂ fluid

WEI Zuojun;LIU Yingxin;NI Jinren

2006, 57(3): 582-589.

Abstract ( 602 )

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A kinetic model for supercritical carbon dioxide extraction was developed by mass conservation calculation of the extraction fixed bed.To determine the model parameter k_La,BP neural network was used to fit the experimental extraction elution curve,which was then compared with the elution curve calculated by the kinetic model with suggested parameter values.The parameter value was eventually determined through trial and error in the fitting process.The results showed that BP neural network could successfully fit the experimental data of the Rhubarb anthraquinone extraction kinetics curves, with 1.5% of training error and 3.5% of prediction error.The kinetic model with determined parameter can be used to describe the extraction bed with higher accuracy. The simulated extraction elution curve through the model had about 10% AARD error compared with the anthraquinone extraction experimental data.This model has the advantage over the others not only for better precision it offers, but also for the fact that it only requires moderate experimental conditions.

SoSolubilization and phase behavior of nonionic water-in-oil microemulsion and its application to extraction of Nd³⁺ in hollow fiber modules

GONG Fuzhong;MA Peihua;LUO Yan;LIU Liheng;ZHANG Limei

2006, 57(3): 590-595.

Abstract ( 774 )

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A nonionic microemulsion(ME) consisted of mixed surfactants named OP-4 ［polyoxyethylene(4)nonylphenol］ and OP-7［polyoxyethylene(7)nonylphenol］, benzyl alcohol, D2EHPA［2-(2-ethylhexylphosphonic acid)］, kerosene as well as HCl solution was prepared.The effects of mass ratio of OP-7 to OP-4,hydrochloric acid concentration,temperature,sodium chloride concentration on the solubilization of HCl solution and the effects of D2EHPA and HCl concentration on phase behaviors were invested.A new membrane-extraction process using the microemulsion as liquid membrane for neodymium extraction in hollow fiber membrane(HFM)was presented for the first time.The results showed out that the content of HCl solution in ME increased with increasing HLB values of mixed surfactants and hydrochloric acid concentrations.But the increase of temperature and NaCl concentration led to a decrease of the content of HCl solution in ME.It also revealed that the WinsorⅡsystem(equilibrium of W/O ME with excess aqueous solution) could form when HCl solution concentration was under 6 mol•dm^-3. While the HCl solution concentration was 7 or 8 mol•dm^-3, however, the Winsor Ⅲsystem(equilibrium of middle ME with both oil and aqueous solution) or the WinsorⅠsystem(equilibrium of O/W ME with excess oil)could form, respectively.As this new membrane-extraction technique was used for the extraction of Nd3+ from 300 mg•dm^-3 feed solution, the extraction percentage reached as high as 95.3% and the concentration in receiving phase was 18.1 fold compared to their initial feed concentration after counter-current extraction with three-modules in tandem.This new membrane system has the advantages of both emulsion liquid membrane and solid membrane extraction.

Solid-liquid separation in micro-fluidic system

FANG Rujian;HOU Liya;ZHANG Weiyi;ZHU Li

2006, 57(3): 596-600.

Abstract ( 617 )

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A new method for solid-liquid separation in micro-fluidic system is proposed on the basis of digital micro-fluid technology.The motion of solid particles in the micro-fluidic channel of micron scale is controlled from the outside of the micro-fluidic system by means of inertial force field produced from the piezoelectric ceramic actuators.Solid-liquid separation is realized due to the velocity difference between micro-fluid and solid particles in the micro-fluidic channel.The separation and selection of solid particles with different density is brought to effect as a result of velocity difference between solid particles in the micro-fluidic channels.It is proved that inertial force still plays a leading role in solid-liquid separation of micron scale.As solid particles usually stick to the surface of the micro-fluidic channels, which leads to difficulty in solid-liquid separation, it is essential to eliminate or weaken the influence of surface force with the aid of surface hydrophobization to the micro-fluidic channels.This method is adopted to drive and separate all kinds of solid particles such as inorganic particles, organic particles and particles with biological activity in the micro-fluidic system, and is especially fit to separate solid particles from high concentration suspension in the micro-fluidic channels which are difficult to separate in other ways.

Physical chemistry study on RO and NF process(Ⅰ) Equations of solute rejection and solution permeation flux on porous membrane

JI Chaoqing;CHEN Hao

2006, 57(3): 601-606.

Abstract ( 742 )

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The equations of solute rejection and solution permeation flux of multi-solute solution on porous membrane were derived on the basis of the adsorption-diffusion model. The physical significance of parameters in the equations was discussed. From the equations of solute rejection and solution permeation flux on porous membrane, the following conclusions were reached: when the solvent was adsorbed preferentially on the membrane surface, solute rejection could decrease as the membrane porosity increased;when the solute was adsorbed preferentially on the membrane surface, three curves of solute rejection vs. membrane porosity were obtained;solute rejection could decrease as membrane porous rate increased;a minimum value was shown on the curve of solute rejection vs. membrane porous rate; a min value and a max value was shown on the curve of solute rejection vs. membrane porosity.The solution permeation coefficient depended on the solute diffusion coefficient and diffusion selectivity of solute with solvent in the membrane phase.Membrane fouling was caused by the fact that the solute was adsorbed preferentially on the membrane surface, leading to increased membrane surface resistance and decreased solution permeation coefficient.

Identification method of gas-liquid two-phase flow patterns based on neural network and D-S evidential theory

ZHOU Yunlong;SUN Bin

2006, 57(3): 607-613.

Abstract ( 766 )

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Based on the neural network and the D-S (Dempster-Shafer) evidential theory, a method was proposed for identifying gas-liquid two-phase flow regimes.Firstly, the differential pressure fluctuation signals were decomposed into 4 levels by the wavelet packet transform.Wavelet packet energy and information entropy of signals in various frequency bands were extracted and two eigenvectors were constructed and then the three statistical parameters and four fractal parameters extracted by the statistical and the fractal theories of the differential pressure fluctuation signals were taken as another eigenvector.Furthermore, the eigenvectors were put into the improved BP neural network and trained to realize the flow regime identification.Taking the preliminary identification as the independent evidence,a final identification was obtained according to the D-S evidential fusion algorithm.Using the air-water two-phase flow regime identification in the horizontal pipe as an example, the implementing process of this method was described in detail.The results showed that the method of multi-characteristic information fusion could achieve a higher identification ability than that of single characteristic.

Filter-SQP in modular simulator environment for process optimization

YUE Jincai, YANG Xia, ZHENG Shiqing, HAN Fangyu

2006, 57(3): 614-619.

Abstract ( 630 )

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Sequential Quadratic Programming (SQP) is the most efficient algorithm for nonlinear optimization.But a penalty function is usually used for linear search,causing some problems.Filter-SQP developed by Roger Fletcher and Sven Leyffer avoids using penalty function.In the view of filter-SQP, NLP problem has two objectives, one is minimizing objective function, the other is satisfying the constraints.The concept of filter is proposed on the basis of these two objectives.In this paper flowsheet optimization using filter-SQP in modular simulator environment was studied.Infeasible path strategy was used and the constraint function was composed of tear stream equation, specific design and unsatisfied inequality constraint.When filter could not find a step as the starting point of the next iteration, in order to avoid algorithm failure three strategies were used.They were restarting strategy, converging recycle strategy and feasible path strategy.A successive scaling strategy was proposed for filter-SQP to improve the efficiency of optimization.A case study of process optimization with filter-SQP was very encouraging.

Reactions of low and middle concentration dry methane on Ni-YSZ anode of SOFC

YOU Hongxin;DING Xinwei; ABULITI Abudula

2006, 57(3): 620-625.

Abstract ( 904 )

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The reactions of low and middle concentration dry methane were studied over the anode of solid oxide fuel cell (SOFC) with Ni/yttria-stabilized zirconia(YSZ) anode and YSZ electrolyte.The production rates of different gases at anode outlet were measured at different current density values.Mass balance and the relation of production rate with reaction rate were used to analyze the chemical and electrochemical reactions taking place in parallel.For low concentration dry methane, partial oxidation of methane occurred at low current density, while electrochemical oxidations of hydrogen and carbon monoxide took place at increased current density.For middle concentration methane，only partial oxidation of methane occurred.Carbon deposition was found in all the tests.

Mechanism and technological foundation of ECM in ultra-pure water

BAO Huaiqian;XU Jiawen

2006, 57(3): 626-629.

Abstract ( 534 )

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In order to develop green manufacturing and microfabrication, an innovative electrochemical machining method was introduced, that is the electrochemical machining(ECM)technology in ultra-pure water.The relative relationship of water dissociation and current density under the function of strong acid cation exchange membrane was studied, and the mechanism of electrochemical machining in ultra-pure water was also explored.On the basis of theoretical analysis, the significance of two turning points of the voltage-current density characteristic curve was presented.As the result of water dissociation and machining experiments, the factors affecting current density were determined.

Separation of fermentation broth of lincomycin by assembled continuous flocculation

DONG Ming;SHAO Qiongfang;LI Jing;CAO Lu;GAO Haoqi

2006, 57(3): 630-635.

Abstract ( 742 )

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Separation of fermentation broth of lincomycin was studied with assembled continuous flocculation and jar testing.The experimental results of jar testing showed that the best concentration of flocculant cationic polyacrylamide in the broth was 70 mg•L^-1.After flocculation, the precipitation rate of the flocs was 24% larger and the filtration rate of the broth was 31% larger by cationic polyacrylamide than by oxalic acid used in the industry.The experimental course of assembled continuous flocculation was modified jar testing，in that the broth was conveyed by a pump and pipeline from fermentation pot to a mixer，in which cationic polyacrylamide and the broth were mixed.Afterward the broth was flocculated continuously in the column，and then the flocs were separated from the broth by filtration or centrifugal precipitation.In the continuous flocculating column，the flux of the broth was 1 L•min^-1，average stay time was 10 min，pH was 3，temperature was 20℃，the concentration of cationic polyacrylamide was 70 mg•L^-1.The experimental results were as follows：the precipitation rate of the flocs in the broth was 46% larger and the filtration rate of the broth was 67% larger in assembled continuous flocculation than in jar testing.The results offer important evidence for flocculated fermentation broth to be separated with high efficiency by filtration or centrifugal precipitation in the industry.

Influence of cosolvents on Photobacterium phosphoreum toxicity test

DONG Yuying;LEI Bingli;MA Jing;WANG Fang

2006, 57(3): 636-639.

Abstract ( 649 )

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There is little information about the influence of organic solvents for low water-solubility organic compounds on Photobacterium phosphoreum toxicity test, though it appears likely that much of data were obtained by using solutions prepared with cosolvents or surfactants.In this study the influence of five stock solvents, including dimethyl sulphoxide (DMSO), acetone, aether, ethanol, tetrahydrofuran, on Photobacteriumphosphoreumtoxicity test was measured and different effective concentration values were obtained.DMSO was selected as the most suitable solvent for organic compounds with low water-solubility according to its good characteristics and less toxicity effect on Photobacterium phospherum.Chlorobenzene and nitrobenzene with proper solubility were selected to verify the effect of DMSO on Photobacteriumphosphoreum toxicity.It was demonstrated that DMSO (concentration no higher than 0.20 mol•L^-1) had little effect on the toxicity of organic chemicals with relative error no more than 10%.The successful application of DMSO as cosolvent provided a good example and a good idea to improve traditional acute toxicity test of Photobacterium phosphoreum, and broadened the application to identifying the toxicity of low water-solubility organic compounds.

High solids loading pneumatic conveying of pulverized coal

GONG Xin;GUO Xiaolei;DAI Zhenghua;FENG Jinhua;CHEN Jinfeng;ZHENG Yaohui;CHEN Feng;XIONG Lang;YU Zunhong

2006, 57(3): 640-644.

Abstract ( 654 )

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High solids loading pneumatic conveying of pulverized coal was achieved in a new pneumatic conveying system where solid/gas mass flow ratio reached 200—580 kg•kg^-1.Operation conditions, including transport pressure,gas volume and pipe diameter were specially designed for the conveying system with pipelines of 15 mm, 20 mm, 32 mm(I.D.) respectively.The effects of different operation conditions on the characteristic parameters, i.e. mass flow rate, solid/gas mass flow ratio and superficial gas velocity, as well as the relationships within the operation conditions themselves, were investigated in the experiments.It was found that under a higher pressure a greater supply of gas was needed, which resulted in greater conveying capacity.However,solid/gas mass flow ratio declined dramatically when solid mass rate increased.The analysis of the experiment also revealed that pipeline diameter was actually the crucial element which brought about great difference in conveying capacity in contrast to the results from the change of operation pressure.Some empirical expressions were finally established which were capable of describing the relationship between the aforementioned parameters and again pipe diameter played an important role.The expressions additionally revealed that gas supply surged with the increase of pulverized coal mass flow rate.The quantitative relations of the parameters might be system-dependent, but this paper presents useful information and approach to pneumatic conveying.

Simultaneous absorbing SO₂ and NO using solution of triethylenediamine cobalt(Ⅲ) coupled with urea

ZHOU Chunqiong;DENG Xianhe;XU Wei;MA Jin

2006, 57(3): 645-649.

Abstract ( 661 )

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Absorption and catalytic oxidation of nitric oxide could be achieved by using Co(en)³⁺₃.When simultaneous absorbing SO₂ and NO, the precipitation of Co₂(SO₃)₃ would be yielded and the NO removal would be decreased.When urea existed in the absorbing solution, the oxidation rate of SO₂^-₃ would be increased and high NO removal would be achieved for a long time.A larger concentration of Co(en)³⁺₃ could increase NO removal rate.The existence of urea could keep a high NO removal rate when simultaneous absorbing SO₂ and NO.A higher NO removal rate and a higher oxidation rate of SO^2-3 could be achieved in the range of 60—70℃.The NO removal rate and SO^2-₃ oxidation rate are controlled by the surface area and coefficient of gas-liquid mass transfer.

Lab-scale pyrolysis of oil sludge in continuous rotating reactor:mass/energy balance and product analysis

CHEN Chao;LI Shuiqing;YUE Changtao;Kruttschnitt T;Pruckner E;YAO Qiang

2006, 57(3): 650-657.

Abstract ( 761 )

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Oil sludge is one of the major industrial solid wastes from petroleum production and refining.Pyrolysis of oil sludge is one of most promising alternative to remove the VOCs (volatile organic compounds) and SVOCs (semivolatile organic compounds) from the solid waste and recover the energy in the gaseous and liquid products, with the minimum pollution to the environment.In this paper, oil sludge was pyrolyzed in a 1—2 kg•h^-1 continuous tubular reactor with internal rotating paddles, which can be regarded as a simplified model of commercial rotary kiln pyrolyzer.The experiments were conducted at 550℃ in argon atmosphere, and mass balance and energy balance were obtained with error no more than 10% and 15%, respectively.About 70%(mass) of solid residue, 20%(mass) of condensate, and 10%(mass) of non-condensable gas were produced.Methane, carbon dioxide, ethane and hydrogen were the major components in the low-calorific gas product (carrier gas Ar included)with calorific value around 11 MJ•m^-3.Physico-chemical properties, distillation fractions, elemental contents, hydrocarbon composition were analyzed for the product oil.Diesel fraction was up to 75% and the calorific value was about 43 MJ•kg^-1 and it could be used as fuel oil directly.However, due to the high contents of S, N, O and PAH, the quality of the fraction was not up to diesel specification.The majority of metal elements were fixed in the pyrolytic residues, while Pb, Cr and Ni were found to be enriched in the fly ash from hot filter.The solid residues contained much sand and inorganic ash.It could be reused as construction material.

Inactivation of Chironomid larvae from drinking water by ozone and its removal using ozone-GAC process

SUN Xingbin;CUI Fuyi;ZHANG Jinsong;ZHAO Kai;LIU Lijun

2006, 57(3): 658-662.

Abstract ( 637 )

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Bench scale experiments were conducted on the inactivation of young Chironomid larvae by ozone, chlorine dioxide and liquid chlorine.Major influence factors on the inactivation effect of ozone were studied.Based on the bench scale experiment results the feasibility of young Chironomid larvae removal by the ozone-granular activated carbon (GAC) process was discussed.It was found that ozone showed better inactivation effect than other two oxidants.Complete inactivation could be reached under the condition of 1.0 mg•L^-1 of ozone with 25 min exposure.The increase in water depth of the reactor was helpful to increasing inactivation rate.COD_Mn greatly influenced inactivation rate in neutral water body.1.0 mg•L^-1 of ozone with 11 min exposure caused complete inactivation of young Chironomid larvae in filtrated water in the dynamic experiment.0.8 mg•L^-1 of ozone combined with GAC treatment was able to entirely eliminate Chironomid larvae with low activity.

Application of two microwave-absorbing materials in microwave assisted oxidation of p-nitrophenol

BU Longli;QUAN Xie;CHEN Shuo;ZHAO Bin;ZHAO Yazhi;ZHAO Huimin

2006, 57(3): 663-669.

Abstract ( 629 )

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Microwave-absorbing ability of granular activated carbon (GAC) and silicon carbide (SiC), and microwave-assisted oxidation of p-nitrophenol (PNP) through the fixed beds of GAC and SiC were investigated. The removal efficiency of PNP with initial solution concentration of 1618 mg•L^-1, reached 96% and 91% of PNP was mineralized onto GAC fixed bed by microwave irradiation, while the highest removal and mineralization efficiency values of PNP were 73% and 24% respectively onto SiC fixed bed for the same PNP solution. Three high concentration PNP solutions (3540, 6858 mg•L^-1 and 11095 mg•L^-1) were treated by microwave respectively through GAC fixed bed and the removal efficiency values of PNP were all higher than 98% and more than 96% PNP was mineralized.The same intermediate products such as o-nitrophenol, phenol and benzoquinone occurred for SiC and GAC during the reaction process, which were degraded further. Biodegradability of the outflow was improved apparently after the treatment by microwave through GAC fixed bed.

Effects of heat treatment on hydriding/dehydriding characteristics of Ti₁₈Cr₂₄V₅₅Zr₃ alloy

CHEN Lixin; LIU Jian;WANG Xinhua;ZHENG Fangping;CHEN Changpin

2006, 57(3): 670-673.

Abstract ( 558 )

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The effects of heat treatment (at 1473 K for 2 h or 6 h) on the hydriding/dehydriding characteristics of Ti₁₈Cr₂₄V₅₅Zr₃ alloy were investigated.The microstructure analysis showed that the as-cast alloy consisted of a V-based solid solution main phase with BCC structure and a ZrCr₂secondary phase, and the alloys treated at 1473 K for 2 h and 6 h had a small amount of Ti-rich phase besides the V-based solid solution and ZrCr₂ phase.It was found that the heat treatment led to an increase of the kinetics of the alloy and a slight decrease of the hydrogen absorption capacity at 20℃.However, the heat treatment increased the width and decreased the gradient of the plateau of the p-c isotherm.The result showed that the alloy treated at 1473 K for 2 h had good overall properties, such as activation behavior of 1 cycle, hydrogen absorption capacity of 394 ml•g^-1 at 20℃ and effective desorption capacity of 232 ml•g^-1 at 80℃.

Improvement of electrochemical performance of LiFePO₄cathode materials for lithium-ion battery

YANG Rong;ZHAO Mingshu;ZHAO Qing;MA Hongli;SONG Xiaoping

2006, 57(3): 674-677.

Abstract ( 645 )

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LiFePO₄ and carbon-doped LiFePO₄ were prepared by a novel solid-phase synthesis.The samples were characterized by X-ray diffraction,SEM,elemental analysis and electrochemical performances.These test results showed that the reaction conditions favored stabilization of samples as well as offered some control of the product morphology.Carbon-doped LiFePO₄ retained olivine structure and had good electrochemical performance.The results of electrochemical evaluation of the doped product showed a lithium insertion plateau around 3.5 V(vs.Li/Li⁺) together with the initial charge specific capacity of 159.9 mAh•g^-1 at 0.1C rate and with little specific capacity decay after 20 cycle at room temperature.

Preparation of higher fatty amines/formaldehyde modified lignin quaternary ammonium salts and measurements of their physico-chemical properties

LIU Zuguang ;CHEN Zhaohui;WANG Dizhen

2006, 57(3): 678-683.

Abstract ( 767 )

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The higher fatty amine/formaldehyde modified lignin quaternary ammonium salts (KL-F-HFA-QASs) cationic asphalt emulsifiers were made by the Mannich reaction and O-alkylation reaction.The effects of some factors on the Mannich reaction were discussed.The experiments showed that the Mannich reaction in dioxane aqueous solution could improve the reaction efficiency obviously.Reaction temperature was 60℃.With increasing octadecylamine dosage, the amount of nitrogen in the modified lignin amines increased.The nitrogen content of modified lignin amines reached a maximum when the molar ratio of formaldehyde to octadecylamine was 1.5∶1.The measurements of physico-chemical properties showed that among different KL-F-HFA-QASs dodecylamine-formaldehyde modified lignin quaternary ammonium salt (KLQAS)solution had the highest surface activity,and smaller surface tension of 33.2 mN•m^-1 that was much lower than 43.8 mN•m^-1 of KLQAS.The emulsifying capacitiy of KL-F-HFA-QASs was improved obviously.Zeta potential of asphalt particles made from dodecylamine-formaldehyde modified KLQASs inceased more rapidly than that of KLQAS.

Model of teminated hydroxy group formation for octamethylcyclotetrasiloxane ring-opening polymerization

ZHOU An’an;WENG Zhixue;SHAN Guorong;HUANG Zhiming;PAN Zuren

2006, 57(3): 684-687.

Abstract ( 670 )

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Hydroxy terminated polydimethylsiloxane (PDMS)was synthesized by using the one-step process via the anionic ring-opening polymerization of octamethylcyclotetrasiloxane (D₄) catalyzed by tetramethyl ammonium hydroxide (TMAH) in the presence of a minute amount of water.Based on the conversion and molecular weight of synthesized polymer determined with gel permeation chromatography (GPC), the teminated hydroxy group concentration (［OH］) of polymer was calculated. According to the mechanism study of teminated hydroxy formation and the transformation of catalyst in the process of polymerization, a kinetic model of teminated hydroxy formation was established.The relationship between chain transfer rate constant and temperature was obtained from the experimental data.The kinetic behavior of teminated hydroxy formation could be predicted by using the kinetic model.

Preparation and properties of polyaniline-poly(propylene oxide)

LI Meichao;MA Chun’an;ZHANG Jingchun

2006, 57(3): 688-692.

Abstract ( 646 )

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Polyaniline(PAN) is one of the most extensively studied materials and attracts great interest from electrochemical viewpoint.However, in order to obtain the most suitable material, the physical and chemical properties of the polymer have to be modified.One of the most important methods is copolymerization.In this paper, a novel copolymer of polyaniline-poly(propylene oxide) (PAN-PPO) film was prepared by cyclic voltammetry for the first time.It was characterized with SEM and thermogravimetric analysis.In addition, the electrocatalytic activity of PAN-PPO for methanol oxidation was investigated.Results showed that under the same conditions, both redox peak currents during polymerization and conductivities of PAN-PPO were higher than those of PAN; the structure of PAN-PPO was a cross-linked network, composed of many uniform and dense nano-fibers with diameter less than 70 nm; the degradation temperature of PAN-PPO was a little lower than that of PAN.In comparison with PAN, PAN-PPO showed a high electrocatalytic activity for oxidation of methanol and the electro-oxidation reaction was controlled by the diffusion step.

Catalytic hydrogenation of furfural to furfuryl alcohol in Pd-Cu membrane reactor

GAO Huiyuan; LI Yongdan;LIN Yuesheng

2006, 57(3): 693-699.

Abstract ( 842 )

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The performance of the membrane reactor (MR) for the hydrogenation of furfural to furfuryl alcohol over a Cu/MgO-K₂O catalyst prepared by the coprecipitation method as a model reaction was studied.The membrane reactor was composed of double-tube and operated with separate feed, i.e., furfural vapor with carrier gas flowed over the catalyst bed in the tube, and hydrogen permeated through Pd-Cu alloy composite membrane from shell side to tube side.The effect on conversion, selectivity and yield was investigated for different parameters such as temperature, hydrogen to furfural feed molar ratio and feed rate.Performance comparison between MR and the conventional packed-bed reactor (PBR) was made.The results showed that MR gave higher yield and better selectivity of the product and less side-products as compared to PBR under the same operation conditions.In addition, on the basis of the information obtained by the characterization of catalyst composition, structure and morphology,activity and deactivation behavior of the catalyst were discussed.

New process of synthesis of propylene oxide

CAO Yinmei;YANG Yiheng;ZHANG Shuangquan;ZHENG Xiaolin;SONG Guoqiang

2006, 57(3): 700-704.

Abstract ( 732 )

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Propylene oxide was synthesized by oxidizing propylene catalyzed by transition metal salts with molecular oxygen in the presence of acet aldehyde under mild condition.This method was safer for the peroxide concentration was maintained at an extremely low level and was convenient and of high yield,as compared with the traditional oxidation methods.The influence of several factors on the reaction was investigated such as the type of catalyst, the ratio of reactants，etc.It was found that when using nickel salt as the catalyst, setting the ratio of acetaldehyde and propylene as 1∶1, reacting 90 min under 70℃,the yield of propylene oxide might reach about 90%.