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Table of Content
25 October 1992, Volume 43 Issue 5
    化工学报
    STEADY STATE MULTIPLICITY FEATURES OF CARBON MONOXIDE OXIDATION REACTION ON PLATINUM CATALYST
    Zhu Jianhua, Liao Hui and Li Shaofen (Department of Chemical Engineering, Tianjin University,Tianjin 300072)
    1992, 43(5):  515-522. 
    Abstract ( 568 )   PDF (428KB) ( 262 )  
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    The steady state multiplicity features of carbon monoxide oxidation reaction on platinum catalyst have been experimentally studied. The experimental results were treated with the help of singularity theory and catastrophe theory, and the number of steady states that were likely to exist was found. In addition, the types of the bifurcation diagram, which describes the relation of state variable to the operation parameters for the reaction system, can be predicted in the operation parameter region having different number of steady states. Finally, it has been realized that it is possible to identify the reaction kinetic model by using the steady state multiplicity features of the system, and a satisfactory result can be obtained.
    CALCULATION OF ACTIVITY COEFFICIENTS BY USING MEAN SPHERICAL APPROXIMATION ( I )FOR SINGLE ELECTROLYTE AQUEOUS
    Yu Yangxin, Lu Jiufang and Li Yigui (Department of Chemical Engineering, Tsinghua University, Beijing 100084)
    1992, 43(5):  523-531. 
    Abstract ( 597 )   PDF (388KB) ( 273 )  
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    The effective diameter of a cation is introduced into the mean spherical approximation(MSA)method. The ionic strength dependence of effective diameter is attributed to the effect of solvation mainly. The effective diameter parameters of the cations have been obtained from regression of the mean ionic activity coefficient data. The range of concentration extends up to saturation when data are available. The modified model has been used to correlate the mean ionic activity coefficients for 85 single electrolyte solutions. The calculated results of the modified mean spherical approximation, original MSA model and Pitzer model are compared with the experimental data. It shows that the modified mean spherical approximation model gives the best representation. The modified mean spherical approximation model has been used to predict the mean ionic activity coefficients at other temperatures by using the parameters obtained at 298.15K. The calculated data show that the temperature dependence of the parameters in this model is smaller than that in the other four models (Pitzer, Bromley, Meissner and Chen).
    CALCULATION OF ACTIVITY COEFFICIENTS BY USING MEAN SPHERICAL APPROXIMATION (Ⅱ)FOR MIXED ELECTROLYTE AQUEOUS
    Yu Yangxin, Lu Jiufang and Li Yigui (Department of Chemical Engineering, Tsinghua University, Beijing 100084)
    1992, 43(5):  532-539. 
    Abstract ( 518 )   PDF (357KB) ( 204 )  
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    The modified mean spherical approximation(MSA)model is used to predict the mean ionic activity coefficients for 32 aqueous mixed electrolyte solutions at 298.15K without any mixing parameters. The results show that the model gives a better representation of mixture properties in terms ofpure component parameters than Pitzers equation without mixing parameters. The mean standard deviation between the calculated and experimental values of 1n γ± is 0.0113. It is close to that of Pitzers equation with mixing parameters. The mean ionic activity coefficients in four mixed electrolyte solutions at saturated concentration and various temperatures have also been calculated by using the parameters obtained from single electrolyte solutions at 298.15K. The agreement between the calculated results and the experimental data is satisfactory over a wide range of temperatures. It shows that the present model has a powerfull capability for predicting the thermodynamic properties of aqueous mixed electrolyte solutions.
    A CUBIC PERTURBED HARD CHAIN EQUATION OF STATE
    Wang Lisheng and Guo Tianmin (Department of Chemical Engineering, University of Petroleum, Beijing 100083)
    1992, 43(5):  540-548. 
    Abstract ( 555 )   PDF (391KB) ( 289 )  
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    For extending the complex perturbed hard chain equation of state to practical engineering calculations, a cubic version is proposed.The new equation is formulated by replacing the repulsive term with a simulated Carnahan-Starling hard sphere equation and combining it with the attractive term in the simplified perturbed hard chain equation of state proposed by Kim et al.The three pure component parameters of 14 n-alkanes and carbon dioxide were determined by fitting the saturated vapor pressure and saturated liquid density data simultaneously over wide temperature and pressure ranges. A new mixing rule has been applied to the energy parameter of the proposed simplified perturbed hard chain equation of state and tested on the vapor-liquid equilibrium and pVT calculations of binary mixtures. Comparisons with four existing equations of state (SPHC, SRK, PR and PT) have been performed.
    METASTABLE PHASE EQUILIBRIUM OF K~+, Na~+, Mg~(2+)//Cl~-,SO_4~(2-)-H_20 QUINARY SYSTEM AT 15℃
    Su Yuguang, Li Jun and Jiang Chengfa (Department of Chemical Engineering, Chengdu University of Science and Technology, Chengdu 610065)
    1992, 43(5):  549-555. 
    Abstract ( 693 )   PDF (330KB) ( 273 )  
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    The experimental data of metastable phase equilibrium of K+,Na+, Mg2+//Cl-, SO42--H2O quinary system at the conditions of temperature 15± 0.1℃, air flowing velocity 3.5-4.0m/s, air relative humidity 35-40%, and evaporation rate 2-4 mm/24h is presented. From these metastable equilibrium data, a metastable phase diagram is drawn. It consists of eight regions of crystallization saturated with sodium chloride: potassium chloride, glasserite, schoenite, carnallite, thenardite epsomite, magnesium sulfate hexahydrate, and bischofit. A model of the K+, Na+, Mg2+ // Cl-, SO42--H2O quinary system is deve theloped for calculating the metastable phase equilibrium. This model utilizes activity coefficient expressions of Harvie and Weare. The calculated data of metastable phase equilibrium fit well with the experimental data.
    ELECTROLYTIC EVOLUTION OF CHLORINE BUBBLES FROM DSA/NaCl SYSTEM
    Chen Yanxi, Shen Manli and Zheng Ping (Department of Applied Chemistry, Tianjin University, Tianjin 300072)
    1992, 43(5):  556-561. 
    Abstract ( 615 )   PDF (327KB) ( 128 )  
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    The chlorine bubble size and distribution electrolytically evolved from DSA/NaCl system were investigated by means of Laser diffraction method. An increase of bubble diameter with increasing current density was observed in the range of 50-300mA/cm2. Electrode orientation and geometry both affected bubble size. When brine concentration was decreased, chlorine bubble diameter became smaller. The results showed that for multi-bubbles system, bubble coalescence might largely determined the bubble size and its distribution.
    MATHEMATICAL MODEL OF HEAT TRANSFER IN GRANULAR MATERIALS
    Liu Xiaoyin (Changsha Research Institute of Mining Metallurgy, Changsha 410012)Mei Chi and Wang Shuqun (Central South University of Technology, Changsha 410012)
    1992, 43(5):  562-569. 
    Abstract ( 655 )   PDF (324KB) ( 168 )  
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    In this paper, the mechanism of heat transfer in granular materials and heat exchange between the bed wall and particles near the wall are investigated. The mechanismic model and two-dimensional pseudo-homogeneous mathematical model of heat trantfer in moving granular materials are presented. Three formulas about the effective thermal conductivity and the wall heat exchange coefficient are derived. The temperature distribution in the moving bed given by numerical solution of the mathematical model agrees with that measured in the experiment. Therefore, the validity of the model and formulas is verified.
    MICRO BEHAVIOR AND HYDRODYNAMIC STRUCTURE NEAR INTERFACE OF A MOVING TURBULENT BUBBLEBY LASER TECHNIQUE
    Miao Rongsheng, Wang Shuying and Yu Guocong(K. T. Yu) (Chemical Engineering Research Center, Tianjin University, Tianjin 300072)
    1992, 43(5):  570-576. 
    Abstract ( 690 )   PDF (376KB) ( 189 )  
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    It is commonly recognized that micro behavior near the interface have considerable significance in the understanding of the mass transfer mechanism in two phase processes. In this work, two dimensional laser doppler anemometer technique has been employed to investigate the hydrodynamics and turbulent structure near the interface of a moving bubble. In our experiment, a bubble was fixed in a specially designed gas-liquid channel with the liquid phase flowing down from top to bottom so as to keep the bubble stationary. It was discovered that in the center of the bubble wake near interface the tangential velocity exhibited large scale coherent structure caused by Karman vortex shedding and the normal velocity showed more stochastic behavior than the tangential. In the edge of the bubble wake, both tangential and normal velocity consisted of the large scale coherent and stochastic vortex. The time averaged normal velocity near rear interface diminished from center to edge of the wake, but the tangential one showed only a little change. The integral scales near rear interface changed appreciably, having maxima in the center of wake and minima in the edge with micro scales remained unchanged. Near the frontal interface, both the tangential and the normal velocities presented regular vibration with the same frequency as the Karman vortex shedding in the bubble wake, while the integral and the micro scales exhibited the same behavior as in the rear interface. The present study on the turbulent behaviors near interface may provide some basic information for understanding the mass transfer mechanism and efficiency in two phase processes.
    SILICA SOL-ORGANIC POLYMER COMPOSITE EMULSION STRUCTURE OF LATEX PARTICLES AND PROPERTIES OF LATEX
    Long Fu, Wang Wei, Xiu Yongshen, Cao Tongyu and Hu Jinsheng (Department of Applied Chemistry, Tianjin University, Tianjin 300072)
    1992, 43(5):  577-582. 
    Abstract ( 725 )   PDF (275KB) ( 132 )  
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    The microscopic structure of the composite latex particles of SiO2-PS/P(BA-MMA-AA) was studied by differential scanning calorimetry, infrared spectrometry and chemical methods. The structural model of the composite particles was put forward and the comprehensive properties of the latex were evaluated.
    APPROXIMATE DYNAMIC DISTILLATION MODELLING BY POLYNOMIAL ORTHOGONAL COLLOCATION
    Huang Kejin, Qian Jixin, Sun Youxian and Zhou Chunhui (Institute of Industrial Control, Zhejiang University, Hangzhou 310027)
    1992, 43(5):  583-591. 
    Abstract ( 853 )   PDF (367KB) ( 115 )  
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    Based on the principle of orthogonal collocation, this paper demonstrates systematically a new methodology for developing a reduced-ordermodel of multicomponent distillation column. The basic column state variables, such as vapor and liquid flow rates and compositions, are considered to be continuous variables along the column.They can be approximately represented by polynomials, thus the number of equations required to describe the system is drastically reduced. As for the discontinuity introduced by the feeds and sidestreams, it can be partially eliminated by suitable redefining new variables which can be approximated by polynomials. In the reduced-order model given in this paper, the simultaneous effects of mass and heat transfer, tray hydraulics and reboiler dynamics are taken into account. The computation time is significantly reduced as the iterative calculation for vapor-liquid equilibrium is avoided. Simulation studies are carried out to check the accuracy of the model for a deethanizer, which has 70 plates and three feeds. It is shown that the model agrees with the rigorous one fairly well.
    EVAPORATION AND INTERFACIAL PHENOMENA OF A SINGLE AEROSOL MICRODROPLET
    Zhang Shouhua,Gao Yong, Zhu Jiawen and Gu Guixin (Chemical Engineering Research Center, East China Institute of Chemical Technology, Shanghai 2000237)
    1992, 43(5):  592-598. 
    Abstract ( 720 )   PDF (351KB) ( 160 )  
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    The electrodynamic balance and light-scattering techniques have been used to study the kinetics of microdroplet evaporation and attendant interfacial phenomena. In the electrodynamic balance a single microdroplet was suspended and adjusted in a polarized laser beam. The scattered light from the microdroplet was detected by a 512-element linear photodiode array and a photomultiplier tube at the scattering angle of 90°. Comparing the light-scattering profile (intensity versus scattering angle) and the resonance spectra with Mie theory, the size and the change of the microdroplet were determined precisely. The techniques have been used to measure the slow evaporation of organic microdroplets, rapid evaporation of water microdroplets, and rapid evaporation of microdroplets of aqueous surfactant solutions. The experimental results show that the interiacial temperatures of rapid evaporation.microdroplets estimated from the data are significantly lower than the surrounding gas temperature; insoluble monolayer formed by surfactant at the microdroplet interface greatly reduces the evaporation rate and microdroplet fission due to interfacial charge effects can occur below the Rayleigh limit, and the charge and the mass loss before and after a fission can be determined by using suspension voltage measurements combined with light-scattering techniques.
    SHELL-SIDE CHARACTERISTICS OF SHELL-AND-TUBE HEAT EXCHANGER WITH SPLITTER-AND-HOLEDIAPHRAGMS
    Zhou Li, An Fu and Xu Yueping (Chemical Engineering Research Center,Tianjin University ,Tianjin 300072)
    1992, 43(5):  599-608. 
    Abstract ( 652 )   PDF (440KB) ( 209 )  
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    The patented novel shell-and-tube heat exchanger with splitter-and-hole diaphragms was designed to enhance heat transfer in the shell-side, whose performance was experimentally examined in the present paper. Compared with the conventional baffle exchangers, it lowers the total shell-side pressure drop to 45% and the pressure drop over the tube bundle to 84%; meanwhile, it gives heat transfer coefficients of 14% higher than the bafflebundle, and 25% higher than the contracted-expanded-tube bundle of type (II), and 88.6% higher than the ROD baffle bundle at the condition of Re = 104. The exchanger with splitter-and-hole diaphragms is shown to be superior to the others in terms of the generalized performance evaluation criteria, such as characteristic ratio of heat transfer, jH factor, convective heat transfer coefficients underlined by equal friction work, and the surface efficiency.
    SIMULTANEOUS OPTIMIZATION OF TECHNOLOGICAL PROCESSES AND HEAT EXCHANGER NETWORKS
    Nie Xiurong and Li Yourun (Department of Chemical Engineering, Tsinghua University, Beijing 100084)
    1992, 43(5):  609-614. 
    Abstract ( 583 )   PDF (339KB) ( 195 )  
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    According to the system engineering theory, simultaneous optimization of technological processes and heat exchanger networks can bring great economic benefits, and it indicates the direction of development in this area. In this paper, a new method called "Superstructure Regression Model" is put forward, it can be used to obtain the optimum flowsheet structure and optimum operation parameters simultaneously. The Superstructure Regression Model is a Mixed Integer Nonlinear Programming (MINLP). In order to overcome the difficulties brought by the discrete variables in the process of optimization, the author proposes a "Integer Variables Continuation Technique" to solve the MINLP problems. At the same time a simplified regression model for ammonia synthesis reactor is brought out in this paper. This method has been used successfully in a fertilizer plants revamping and expansion project.
    EFFECT OF NUCLEATING AGENT ON TRANSPARENCY AND CRYSTALLINE MORPHOLOGY OF ISOTACTIC POLYPROPYLENE
    Zhang Quan, Shi Yongxi, Wang Hongpeng, Li Yang and Li Yu (Beijing Institute of Chemical Technology, Beijing 100029)
    1992, 43(5):  615-620. 
    Abstract ( 716 )   PDF (444KB) ( 309 )  
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    The crystalline morphology of two kinds of nucleating agent- 1.3,2.4-di (p-methoxybenzylidene) sorbitol (DOS) and 1.3,2.4-dibenzylidene sorbitol (DBS) was studied. The new-synthesised nucleator-DOS effect on Isotactic polypropylene(IPP)crystaline morphology was also investigated. The SEM micrograph of DBS showed that the formation of DBS dulling rings was due to the connected cracks of DBS lamellae. Both DOS and DBS formed negative spherulites similar to those of IPP/DOS had a notable effect on the IPP surface crystals. There were spherulites formed on pure IPP film and the pebbled crystals were formed on IPP surface with the addition of a small amount of DOS. Compared with DBS, less amount of DOS was used and better transparency could be obtained.
    CYLINDRICAL CENTRIFUGAL EXTRACTOR FOR EXTRACTION PURIFICATION OF α-AMYLASE IN AQUEOUS TWO-PHASE SYSTEMS
    Fung Youqin, Mei Lehe, Zhu Ziqiang and Chen Xiaoguo (Department of Chemical Engineering, Zhejiang University, Hangzhou 310027)
    1992, 43(5):  621-626. 
    Abstract ( 523 )   PDF (329KB) ( 118 )  
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    The technical aspects of a new and powerful separation technique, extractive purification by aqueous two-phase systems were studied in detail. According to the characteristics of aqueous two phase systems, a φ20 cylindrical centrifugal extractor was selected as the equipment for extractive purification of α-amylase. The hydraulic characteristics of the installation and the effects of speed and total throughput on the yield and Murphree efficiency of α-amylase extraction were investigated. A speed of 3380-3800r/min, a flow ratio of 0.2-0.5 and a total throughput of 25-50ml/min were found as the optimal operation range for while 90% of phases purity, 75% yield and 90% Murphree efficiency for a-amylase could be obtained.
    GAS HOLD-UP AND OXYGEN TRANSFER COEFFICIENT OF NON-NEWTONIAN FLUID IN A RECTANGULAR CHANNEL AIR-LIFT BIOREACTOR
    Ouyang Pingkai and Zhu Huajie (Department of Applied Chemistry, Nanjing Institute of Chemical Technology, Naniing 210009)
    1992, 43(5):  627-634. 
    Abstract ( 494 )   PDF (313KB) ( 174 )  
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    A rectangular channel air lift bioreactor, which has good properties of mass transfer and hydrodynamics, better operation sensitivity than traditional ALR, was studied. The parameters of KLa and εg of mass transfer and hydro dynamics were experimentally studied by using CMC aqueous solutions of different concentrations. The research showed that when the rheological properties of pseudoplastic non-Newtonian fluid could be described by τs=ηγn thus By using the above correlation, the performance of the bioreactor was discussed with regard to the structure of reactor, fluid properties, and operation condition.non-Newtonian fluid, rectangular air-lift reactor, gas hold-up, mass transfer coefficients
    CONCENTRATION FIELDS AND MASS TRANSFER BEHAVIOR NEAR A MOVING BUBBLE INTERFACE BY LASER TECHNIQUE
    Miao Rongsheng, Wang Shuying and Yu Guocong(K. T. Yu) (Chemical Engineering Research Center, Tianjin University, Tianjin, 300072)
    1992, 43(5):  635-639. 
    Abstract ( 549 )   PDF (289KB) ( 187 )  
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    A laser holographic interferometer with optical magnification was designed and used in this work for the study of concentration fields near the interface and mass transfer phenomena of a gas bubble moving against a countercurrent liquid stream. The concentration profiles in liquid phase near the frontal and rear interfaces of a bubble were measured quantitatively for the systems containing carbon dioxide as gas phase and methanol, ethanal and n-propanal as liquid phase respectively. It was found that the liquid phase concentration at a close distance to the interface in the order of 10-2mm, designated as quasi-interface concentration, was far from the thermo-dynamic equilibrium value. The concentration fields near the frontal and rear interfaces differed considerably, and such differences were affected by both the liquid phase velocity and equivalent diameter of the bubble. Inner circulation within a bubble was viewed from the hologram in the bubble formation stage, and it disappeared soon afterwards. Experimental results were discussed from the basic mass transfer equation by means of scale analysis.
    VAPOR LIQUID EQUILIBRIA FOR N_2-CH_4-CO_2 SYSTEM NEAR CRITICAL REGION
    Xu Nanping, Dong Junhang, Wang Y&nru and Shi Jun (Nanjing Institute of Chemical Technology, Nanjing 210009)
    1992, 43(5):  640-644. 
    Abstract ( 463 )   PDF (205KB) ( 162 )  
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    Vapor liquid equilibria data were measured for N2-CO2 binary system at 298.43K and for CH4-CO2 system at 298.35K. Ternary vapor liquid equilibria measurements were made for the system N2-CH4-CO2 at 298.3K and 7.25, 7.73 and 8.05 MPa. The data obtained in this work and literature data available on these systems wer ecorrelated by the modified Peng-Robinson equation of state.