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Table of Content
25 April 2001, Volume 52 Issue 4
    综述与专论
    PROGRESS IN STUDYING OF DRYING OF SOLVENT-COATED POLYMER FILMS
    XIA Zhengbin;TU Weiping;YANG Zhuoru;CHEN Huanqin
    2001, 52(4):  283-287. 
    Abstract ( 666 )   PDF (912KB) ( 212 )  
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    The present knowledge about the formation process of solvent-coated polymer films and its mechanism of drying are reviewed in this paper. In order to understand and analyze drying process, optimize the design of dryers, modeling the drying process has been an important research directions. However,it is very difficult to obtain all necessary data, especially the data of diffusion coefficients. Vrentas-Duda free-volume theory is regarded as an efficient tool in estimating the diffusion coefficient of solvents in a binary polymer-solvent system. According to the development in modeling the drying of polymer films, formation of drying defects, and measurement or calculation of solvent diffusion coefficients in coating systems, the areas which represent opportunities and needs for further study on the drying of coatings film are also discussed.
    研究论文
    SELECTION OF POLYMER SOLVENTS AND NEW TWO-DIMENSIONAL SOLUBILITY PARAMETER
    YU Chunfang;HEI Encheng;LIU Guojie
    2001, 52(4):  288-294. 
    Abstract ( 873 )   PDF (832KB) ( 452 )  
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    Based on the new definition of solubility parameter obtained by our previous work, a new two-dimensional solubility parameter consisted of the physical and chemical (solubility parameter) components has been established. The method proposed by Wiehe is used as a reference to divide the two components. From the profile of solubility data, it can be seen that all solvents are almost located within some area of solubility parameter diagram for every polymer. This area can be expressed by an ellipse, which provides an important basis for the selection of polymer solvents. Using a simple adding rule, it can be satisfactorily used to predict the solvency of mixing solvents. The results of extensive testing show that the new two-dimensional solubility parameter is more reliable than Hansen’s three-dimensional solubility parameter for the selection of polymer solvents.
    OPTIMAL GRADE TRANSITION IN CONTINUOUS POLYMERIZATION PROCESS
    WANG Jingdai;CHEN Jizhong;YANG Yongrong
    2001, 52(4):  295-300. 
    Abstract ( 755 )   PDF (724KB) ( 149 )  
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    A model of grade transition is presented for the commercial fluidized bed gas-phase polyethylene production process. For two polyethylene products,the model-based dynamic optimization is used to determine optimal grade changeover policies. The quantity of off-specification product and the time of grade transition can be minimized by optimization of manipulated variable profiles, such as polymerization temperature, the ratio of hydrogen to ethylene, the ratio of co-monomer to ethylene, catalyst feed rate, and bed level. The results show that polymerization temperature, hydrogen and co-monomer are sensitive to the quality of resin. It is always recommended that catalyst feed rate and bed level decrease in order to reduce the grade transition time and the quantity of off-specification product. It is demonstrated that melt index and density are not sufficient to characterize the properties of polymer produced during grade transition. A new performance index, i.e. ratio of melt flow ( MFR ), is included into the objective function, which could restrain the sharp fluctuation of operation variables and narrow the distribution of molecular weight of resin. There are much difference between the transition and reverse transition of grade which indicates the non-linearity of operation.
    EFFECTS OF MASS AND HEAT RECOVERY ON PERFORMANCES OF ACTIVATED CARBON/AMMONIA ADSORPTION REFRIGERATION CYCLES
    QU Tianfei;WANG Ruzhu;WANG Wen
    2001, 52(4):  301-305. 
    Abstract ( 654 )   PDF (696KB) ( 124 )  
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    Mass recovery in activated carbon/ammonia adsorption cycle can play an important role to better the performance of refrigeration cycle. Coefficient of performance might increase or decrease with mass recovery process due to different working conditions. Cooling capacity per kg of adsorbent can be significantly increased with mass recovery process. And the effects of mass recovery do not vary much due to different operating conditions. The effect of mass recovery on cooling capacity does not vary with heat capacity of thermal fluid and bed metal. The higher the condensing temperature is, the more the cooling capacity of mass recovery cycle will be improved. The cycle with mass and heat recovery has a relatively higher COP . It can also be seen that the cycle time will be much shorter and it will certainly enhance the cycle with higher cooling/heating power.
    EFFECTIVE DIFFUSIVITIES OF GAS DIFFUSION IN POROUS ALUMINAS
    XIN Feng;YIN Xiaohong;WANG Fumin;LIAO Hui;LI Shaofen
    2001, 52(4):  306-310. 
    Abstract ( 711 )   PDF (614KB) ( 335 )  
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    Wicke-Kallenbach steady state diffusion experiment of binary and ternary diffusions of ethylene,argon and carbon dioxide were carried out in two kinds of alumina.The flux equations were established based on the dusty-gas model and Stefan-Maxwell equation and used to interpret the experiment data.The effective diffusivities for binary diffusion and pseudo binary effective diffusivities for ternary diffusion were obtained.At the meantime,the basic condition was derived to treat the effective diffusivities as constant for isothermal binary transient diffusion,which is identical with the experiment results.However,for ternary diffusion the pseudo-binary effective diffusivities can not be taken as invariable.In addition,for each alumina there is almost the same tortuosity no matter whether binary or ternary diffusion is,so tortuosity is a parameter that has a close relationship with the structure of porous media.
    INVESTIGATIONS ON ION EXCHANGE CHROMATOGRAPHY CONDUCTED IN ALTERNATING ELECTRIC FIELD
    WANG Donghai;LIU Zheng
    2001, 52(4):  311-315. 
    Abstract ( 626 )   PDF (721KB) ( 144 )  
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    The chromatographic separation of BSA on DEAE-Sepharose Fast Flow in an alternating electric field is studied with emphasis on the adsorption and desorption kinetics and mass transfer characteristics. The experimental results show that, within the range of the electric field strength applied in the experiments described in this study, the application of the electric field has not shown a significant effect on ion exchange isotherm. However, the transport of the biological molecules among the liquid and solid phases can be greatly enhanced by electroosmosis generated inter- and intra-particle. This leads to an increased dynamic binding capacity and available bed volume for adsorption, consequently. The application of the alternating electric field also improves the elution peak properties described by the ratio of peak height to peak width and this is essential for obtaining a high resolution.
    TEMPERATURE MATCHING FOR CFB REACTOR SYSTEMS FOR SELECTIVE OXIDATION OF N-BUTANE TO MALEIC ANHYDRIDE(Ⅱ) PERFORMANCE SIMULATION,ANALYSIS AND TEMPERATURE MATCHING
    LIU Hui;HUANG Xiaofeng;LI Chengyue;CHEN Biaohua
    2001, 52(4):  316-321. 
    Abstract ( 675 )   PDF (664KB) ( 364 )  
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    Based on the models and computation method developed in the part (Ⅰ),this paper analyses the effects of operation conditions on the time dependent variations of different kinds of oxygen and the performance of the CFB reactor system. The simulation and analysis lead to the following conclusions regarding to the performance of the riser-regenerator two bed system for selective oxidation of n-butane to maleic anhydride over the VPO catalyst. The reaction performance in the riser is strongly influenced by gas phase feed compositions and solid phase oxygen loading. It is also demonstrated that an improved selectivity and yield for maleic anhydride can be achieved by elevating regeneration temperature so as to enhance the oxygen uptake rate and to optimize distribution of different types of oxygen sites over the catalysts. At the same time, the solids circulation flux through the system can largely be reduced.
    SPARSE SQP ALGORITHM FOR CHEMICAL PROCESS OPTIMIZATION
    ZHONG Weitao;SHAO Zhijiang;ZHANG Fan;ZHANG Yuyue;QIAN Jixin
    2001, 52(4):  322-326. 
    Abstract ( 846 )   PDF (612KB) ( 304 )  
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    Chemical process optimization problems based on the open-equation modeling approach are frequently characterized by large sparse models. To solve large-scale on-line optimization problems, efficient and reliable optimization algorithms should be developed and considered. In this paper, a full space sparse SQP algorithm is presented. First/second finite derivatives are used to build Jacobian and Hessian matrices,while the inherent sparse structure existing in systems is maintained. A preprocess is employed to exploit the sparse structure. Through this phase, the elements in Jacobian and Hessian matrices are divided into two parts: zero and nonzero ones. Only nonzero elements are computed in the algorithm. Moreover, to reduce the computing time for Jacobian and Hessian matrices, the constants are identified and withdrew from nonzero elements. Those constant elements are stored as global variables so that they can be called at any time without being computed in each iteration. Thus the computational demands and storage requirements for large matrices could be reduced. Compared with traditional SQP algorithm, the performance of this algorithm is enhanced significantly. These enhancements are demonstrated on a number of test problems, including scalable mathematical problems and chemical optimization problems. Computing results indicate the possibility and efficiency of this algorithm for the large-scale on-line optimization of chemical process systems.
    EXPERIMENTAL INVESTIGATION OF DYNAMIC LIQUID HOLDUP UNDER PULSE FLOW IN TRICKLE-BED REACTOR
    XIAO Qiong; A.M.ANTER; CHENG Zhenmin; YUAN Weikang
    2001, 52(4):  327-332. 
    Abstract ( 671 )   PDF (766KB) ( 288 )  
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    The theoretical analyses of the hydrodynamics under a strong interaction flow regime were conducted and data of the bed averaged dynamic liquid holdup were obtained.The influence of gas and liquid velocity, liquid viscosity and packing materials on dynamic liquid holdup was investigated. The liquid superficial velocity has less significance on liquid holdup than gas superficial velocity.Actually it affects liquid holdup,especially under a mild pulsing flow regime.Liquid viscosity has no significance on liquid holdup,compared to gas and liquid phase velocity.The properties of the packed materials,such as lubricity,roughness etc.,were found to have a strong effect on liquid holdup.Based on the experimental data and theoretical analyses a new variety of correlation was proposed for dynamic liquid holdup under pulse flow,which was expressed as βd=1.3242· γ · Re 0.05666 L· Re -0.3324 g(for ceramic beads γ =1.0 and glass beads γ =1.42).The equation correlated the experimental data well and had good reliability in predicting dynamic liquid holdup under mild pulse flow.
    MATHEMATICAL MODELING OF LOW-TEMPERATURE LIQUID PHASE METHANOL SYNTHESIS PROCESS IN A BUBBLE SLURRY REACTOR
    LV Zhaohui;ZHAO Liangfu;ZHAO Yulong;ZHANG Kai
    2001, 52(4):  333-337. 
    Abstract ( 590 )   PDF (601KB) ( 243 )  
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    Due to the concurrence of carbonylation of methanol and hydrogenolysis of methyl formate(MeF)in a slurry reactor,methanol synthesis via MeF has the following advantages:low reaction temperature,high per pass conversion,good heat transfer and direct utilization of crude methanol product as fuel,thus it is a more efficient and more economic methanol production process than the conventional methanol process.In this presentation,a model of the low temperature methanol systhesis(LTMS)via MeF in a bubble column slurry reactor(BCSR)is presented.The model assumes:the gas phase being in plug flow and unmixed slurry phase,catalyst concentration distribution is described by the sedimentation-dispersion model.Liu’s non- linear reaction kinetic expression for LTMS over G-89 catalyst is used in the present model.The effect of various operating variants which include temperature,pressure,superficial gas velocity and catalyst concentration on the reactor productivity are studied.Computation results show that the higher the reaction temperature,the higher the equilibrium conversion and productivity of methanol.Increasing the gas superficial velocity leads to a gradual drop in syngas conversion,while STY goes through a maximum.Under slurry operation condition,high catalyst concentration increases the viscosity of slurry which tends to form large bubbles and,in return,also decreases gas-liquid interfacial area and the residence time of gaseous components in reactor,which affects the efficiency of reactor.
    MECHANISM OF REACTION OF METHANOL AND ISOBUTENE OVER ZEOLITE HBT6
    LI Yonghong;YU Shaobing;HAN Sen;CHEN Hongfang;MIN Enze
    2001, 52(4):  338-342. 
    Abstract ( 881 )   PDF (640KB) ( 179 )  
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    The adsorption of methanol, isobutene and MTBE on zeolite HBT6 was investigated using IR spectroscopy. The mechanism of synthesis of MTBE from methanol and isobutene over zeolite HBT6 was studied based on adsorptive states of reactants and product over the catalyst and intrinsic kinetic experiments. Methanol, isobutene and MTBE were probably adsorbed on OH groups of the zeolite, and adsorbed isobutene molecules were π-complexes which could, easily, turn into tertiary butyl C +. Reaction of methanol with isobutene over the zeolites takes place according to the L-H mechanism and the rate-determining step is the reaction of adsorbed methanol with adsorbed isobutene. TPD following adsorption showed that some of the methanol molecules were strongly adsorbed on the catalyst. It might be a disadvantageous factor.
    MODELING AND SIMULATION OF GAS-LIQUID-SOLID THREE-PHASE TURBULENT FLOW BASED ON E/E/L MODEL
    WEN Jianping;HUANG Lin;ZHOU Huai;YU Baotian;HU Zongding
    2001, 52(4):  343-348. 
    Abstract ( 638 )   PDF (664KB) ( 194 )  
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    A closed Eulerian/Eulerian/Lagrangian mathematical model(E/E/L model) for simulating gas-liquid-solid three-phase local flow was established by combining Two Fluid Model(TFM) and District Element Method(DEM).This model was based on the fundamental equations of fluid mechanics. The motion of particles was described in the Lagrangian coordinates, while the gas phase and the liquid phase were dealt with in the Eulerian coordinates.Based on IPSA and PSIC solution techniques, the program of simulating gas-liquid-solid local flow was achieved. The predicted results of local gas holdup and local solid holdup as well as local axial liquid velocity agreed well with the experimental data in gas-liquid-solid three-phase fluidized bed,and the applicability and reliability of this model were validated.
    研究简报
    SOLUBILITIES OF CO2 IN BIOMIMETIC AND OTHER ABSORBENTS
    GONG Gangli;WANG Xiangyun;ZHANG Zhibing
    2001, 52(4):  349-353. 
    Abstract ( 574 )   PDF (570KB) ( 160 )  
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    Biomimetic CO2 Absorbent is a novel solvent for CO2 removal, which is derived from the key group of respiratory enzyme in animal bodies.The solubility performance of this substance is between physical and chemical absorbents and is suitable for process conditions which physical or chemical absorbents cannot match ideally.In this paper, CO2 solubilities in several typical absorbents including pure biomimetic absorbent, mixed biomimetic absorbent, AMP solution and NMP have been measured.The results show that the pure biomimetic and mixed biomimetic absorbents have good thermodynamic performance and prospective industrial application.

    MOLECULE DYNAMICS SIMULATIONS OF THERMAL CONDUCTIVITIES OF STRUCTURE H HYDRATE
    WANG Lukun;CHEN Guangjin; Ronald M.PRATT; GUO Tianmin
    2001, 52(4):  354-356. 
    Abstract ( 686 )   PDF (369KB) ( 253 )  
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    Molecule dynamic simulation was carried out to predict the thermal conductivity of structure H hydrate at 100K,180K and 260K. In order to get a reliable potential model and stable simulation method the simulations of thermal conductivities of ice and empty hydrate were performed firstly at 100K, 180K and 260K. The simulation results of ice, empty hydrate and structure H hydrate show that thermal conductivities of ice and hydrates have different temperature dependence: for structure H hydrate it is not so distinct while that of ice is inversely proportional to temperature.

    MODIFIED POLANYI-DUBININ EQUATION TO CORRELATE ADSORPTION EQUILIBRIUM OF VOC-WATER VAPOR MIXTURES ON ACTIVATED CARBON
    GAO Huasheng;WANG Dahui;YE Yunchun;TAN Tianen
    2001, 52(4):  357-362. 
    Abstract ( 764 )   PDF (740KB) ( 228 )  
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    Long-column method was used to determine the adsorption isotherms of 4 VOCs (benzene, toluene, chloroform and acetone) in concentration range of 250~5000mg·m-3 on a commercial activated-carbon under different humidity levels at 30℃.A modified Polanyi-Dubinin equation was proposed to correlate the adsorption equilibrium of different VOC-water vapor systems. Among 3 methods of calculating the Relative Affinity Coefficient β used,the Molar Volume method and the Molecular Parachor method proved to be suitable for the calculation with better precision than the Electronic Polarization method. Calculation results were satisfactory for the benzene-, toluene-, and chloroform-water vapor/activated carbon systems, but poor for acetone possibly because of its strong polarity.The equation could be used to estimate the detaining effect of atmospheric humidity on the adsorption equilibrium of VOCs on activated carbon.
    CALCULATING ACTIVITY COEFFICIENTS OF ELECTROLYTE AQUEOUS SOLUTION WITH PERTURBATION THEORY-BASED EQUATION OF STATE
    LI Chunxi;SONG Hongyan;LI Yigui;LU Jiufang
    2001, 52(4):  363-367. 
    Abstract ( 673 )   PDF (589KB) ( 345 )  
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    An equation of state for electrolyte aqueous solution is developed by treating the ion-ion electrostatic and ion-solvent molecule interactions with primitive MSA and perturbation theory, respectively. The effect of the dielectric constant on the ionic chemical potential and the calculation accuracy of ionic mean activity coefficients for 2∶1 and 1∶1 type halide aqueous solution are discussed.By taking ionic Pauling diameter as ionic hard sphere diameter for anions and treating the cation hard sphere diameter as ionic strength dependent, the equation can be used to calculate ionic activity coefficients in the moderate concentration range with good accuracy.
    INTENSIFYING DISTILLATION OF CRUDE OIL BY USING NEW ACTIVATOR
    LIU Hongyan;SHA Feng;ZHAN Yali;ZHU Jianhua
    2001, 52(4):  368-371. 
    Abstract ( 728 )   PDF (570KB) ( 165 )  
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    By using activator to change the state of crude oil and to diminish the size of dispersed phase,mass transfer in distillation process is intensified and distillate yield is increased.In this work,the new activators R1 and R2 were used as the additives respectively,and the intensifying effects to Daqing crude oil were examined at different concentrations and liquid phase temperatures by means of simple distillation and TBP distillation.The interaction mechanisms between the new activators and the crude oil or residues were analyzed,the intensifying effects by the new activators were also studied.Finally,the conceptual technique of “chemical intensification distillation”was put forward.
    DEGRADABLE BEHAVIORS OF LACTIDE CHAIN-EXTENED POLYMERS
    FENG Duanjiang
    2001, 52(4):  372-375. 
    Abstract ( 580 )   PDF (511KB) ( 111 )  
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    In this paper,the effects of change of degradable rate and relative molecular mass on the degradable behaviors of four lactide chain-extened polymers are contrasted with those of lactide polymers.The results indicated that the four lactide chain-extened polymers could degrade in this experiment and their degradable rate were lower than that of P-LA.LA-SDI has the highest degradable rates among the four lactide chain-extened polymers,but there was no significant difference among aromatic and aliphatic lactide chain-extened polymers.The results showed that the degradable rates were dependent on experiment methods and condition and also indicated that the relative molecular mass became smaller and smaller with the progress of degradation time.