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Table of Content
25 September 1985, Volume 36 Issue 3
    化工学报
    Kinetic Modeling of Hydroisomerizationof C_8-Aromatics( I ) Modeling and Estimation of Relative Rate Constants by the Wei-Prater Method
    Wu Dengxi and Lin Zhengxian(C. S. Lin) (Research Institute of Petroleum Processing)
    1985, 36(3):  257-267. 
    Abstract ( 533 )   PDF (578KB) ( 145 )  
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    Hydroisomerization of C8-aromatics on bifunctional catalysts is a main approach to commercial production of paraxylene. In the present paper, the selectivity kinetics of hydroisomerization of C8-aromatics on a Pt/zeolite catalyst has been investigated at 380℃, 886kPa, and H2/hydrocarbon ratio of 10 conditions similar to industrial operation. The apparent chemical scheme, in which C8-naphthenes in the reaction system is regarded as a lumped species, is proposed, and the kinetic model for the Hougen-Watson type pseudomonomolecular system is used. The relative rate constant matrix is estimated by the Wei-Prater method. The results explain the reaction mechanism reported in the literature, and fit experimental data. Expressions for purging composition data and row vectors of inverse of modal matrix, which are helpful in simplifying calculation, are developed.
    Kinetic Modeling of Hydroisomerizationof C_8-Aromatics(Ⅱ) Mathematical Expression of Ray Vector andIts Application
    Wu Dengxi and Lin Zhengxian(C. S. Lin) (Research Institute of Petroleum Processing)
    1985, 36(3):  268-277. 
    Abstract ( 679 )   PDF (493KB) ( 96 )  
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    For Ma subsystem in a complex monomolecular reaction system containing irreversible reactions, the character of the only observed straight line reaction path in two dimensional coordinates is observed. A mathematical expression of ray vector as an implicit function of rate constants is derived. Taking advantage of the expression as a set of linear equality constraints, the relative rate constant matrix of hydroisomerization of C8-aromat-ics is estimated by means of flexible tolerance polyhedron. It is proved that the uncertainty of curve-fitting can be reduced because of these constraints. It provides an effective resort for parameter estimation of Ma monomolecular subsystem.
    Exact Calculation Methods of Interlinked ColumnSystems——Simulation of Recovery ofPhenol from Waste Water
    Xu Xien and J. W. Tierney (Chem. Eng. Dept. Tianjin University) (Chem. Eng. Dept. University of Pittsburgh, USA)
    1985, 36(3):  278-288. 
    Abstract ( 565 )   PDF (536KB) ( 120 )  
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    This paper describes a mathematical model and an algorithm which can be used for simulation of interlinked column systems consisting of liquid-liquid extraction and distillation. This algorithm is based upon Newton-Raphson iteration technique using suitable damping factors and solutions of a simplified version of model as initial values of exact calculations. With the exception of principlal specifications it is possible to exchange the iteration variables and/or noniteration variables with the design variables to meet requirements of design. A process of recovery of phenol from waste water is illustrated to verify the model and algorithm.
    An Algorithm for Complex Distillation Column Design Calculation
    Zhang Kecheng and Guo Tianmin (Beijing Graduate School of The East China Petroleum Institute)
    1985, 36(3):  289-301. 
    Abstract ( 632 )   PDF (523KB) ( 367 )  
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    A new generalized algorithm for design calculation of various kinds of complex distillation columns(with multiple feeds, vapor and liquid phase side withdrawals and intermediate heat exchangers) has been developed. Based on specified independent variables: conditions of feeds, yields of light and heavy key components, yield and concentration of specified component in side-cut product, etc., a set of optimum design variables (reflux ratio, number of equilibrium stages required, feeds and sidewithdrawals locations, etc. )were determined by optimization technique. This new algorithm as coupled with the SHBWR or PR model for vapor-liquid equilibrium and enthalpy calculations, has been tested on five-light hydrocarbon complex distillation columns(including three field operating columns), with quite satisfactory results.
    An Approximate Mathematical Model for Design of Industrial Crystallizers with Elutriators
    Qian Ruying and Chen Zude (Shanghai Research Institute of Chemical Industry)
    1985, 36(3):  302-311. 
    Abstract ( 528 )   PDF (479KB) ( 209 )  
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    In spite of the effect of cycling on crystal size distribution(CSD) of potassium chloride in a pilot plant crystallizer, the average size can still be simulated by a steady-state mathematical model. According to this model, the CSD in the main size range for industrial crystallizers may be expressed as an exponential function of the population density n with respect to crystal size L, as for mixed-suspension-mixed-product-removal (MSMPR) crystallizers. For fine and coarse crystals, the withdrawal of fines and the classification of coarse crystals, respectively, should be taken into account as in the case of the R-Z model. For intermediate crystals, which can settle behind the baffles and can not be drawn off effectively from the elutriator, their retention time is taken to be infinite for simplification. The resulting mathematical model is expressed by Eqs. ( 2 )-( 5 ) and illustrated in Fig. 2. This model is a generalized form of all previous models for crystallizers. The calculated CSD in the main-size range fits well data from a 520-liter pilot-plant crystallizer. The calculated values for crystal growth rate G, dominant crystal size LD, median crystal size L50, suspension density MT, and production rate P/V, all agree, within 10%, with the corresponding experimental data. However, the MT equation, Eq. (10), is rather complicated, so a. simplified model, in which LF = 0 and Z = ∞, is derived, and a simplified MT equation, Eq. (11), is used for crystallizer design. The design Procedure for industrial crystallizers with elutriators is also given.
    A New Decomposition Strategy farInformation Flow Nets
    Zhou Li (Chemical Engineering Research Center, Tianjin University)
    1985, 36(3):  312-322. 
    Abstract ( 459 )   PDF (512KB) ( 131 )  
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    Decomposing the information-flow net is the first task in process simulation of a complex process flowsheet. Among the efforts since the 1960s dedicated to this subject for finding the best set of tear streams that guarantees fast convergence and minimal computation time, most strategies involve two stages of decomposition, namely, indentification of loops in the net, and tearing them afterwards. The optimal solution of the decomposition problem usually cannot be obtained without considerable expenditure of computation time. The new method for decomposition of nets in this paper avoids the need of identification of loops and any matrix operation. By converting two-dimensional net to a onedimensional node sequence according to the decreas ing magnitude of "node weights", which can be easily counted in terms of the adjacent matrix of the"joint nodes", each of which connects three or more streams, followed by adjusting the node positions in the sequence in such a way that the total of weights of counter-streams decreases after the adjustment, one quickly reaches the optimal set ef tear streatns and the final node sequence, which determines the computation order in simulation. The decomposition procedure and its advantage are demonstrated by seven examples commonly referred to.
    Calculation of Thermodynamic Properties of RealFluids and Vapor-Liquid Equilibria byUsing a Canonical Partition Function( I ) Thermodynamic Properties of Pure Fluids
    Zhang Changqun, Zhan Chuanjun and Bai Shouli (Beijing Institute of Chemical Technology)
    1985, 36(3):  323-330. 
    Abstract ( 569 )   PDF (361KB) ( 93 )  
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    The Anderson-Prausnitz equation of state has been improved by modifying the attractive term of the generalized van der Waals canonical partition function. In this modification, the parameter characterizing the intermolecular attractive forces is considered to depend not only on temperature but also on density. The calculated results for pressure and fugacity of pure gases, and for saturated vapors and saturated liquids, by using this new equation of state are in good agreement with observed results. Extension to mixtures and multicomponent vapor-liquid equilibria will be presents in Part 2.
    Vapor-Liquid Equilibrium Calculations with Peng-Robinson Equation of State and the Conformal Solution Mixing Rules
    Wang Wenchuan (Lanzhou Research Institute of Chemical Machinary)
    1985, 36(3):  331-338. 
    Abstract ( 1030 )   PDF (367KB) ( 502 )  
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    The Peng-Robinson equation of state was used for predicting vapor-liquid equilibria for three binary groups-methane-hydrocarbons, carbondi-oxide-hydrocarbons, and hydrogen-hydrocarbons. The correlated interaction parameters were recommended for binary systems containing methane and carbon dioxide. Application of the conformal solution mixing rules and a proposed correction of the temperature dependent factor a to highly asymmetric hydrogen-containing binary system, led to a more accurate description of vapor-liquid equilibria than the original work of Peng-Robinson.
    Gas-Liquid-Interphase Mass Transfer Coefficients in Trickle Beds
    Chen Zhongliang, Cai Yunsheng and Li Pangsheng (East China Institute of Chemical Technology)
    1985, 36(3):  339-346. 
    Abstract ( 604 )   PDF (406KB) ( 464 )  
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    Gas-liquid-interphase mass transfer coefficients kLa were measured for CO2-air-water and H2-air-water systems in a trickle bed with gas and liquid flowing cocurrently downward. Glass heads with diameters dp 0.0065, 0.00475 and 0.00154 m were packed in a column of 0.042 m inside diameter. The gas-phase superficial velocities uG were 0.12-0.56m/s, and the liquid-phase superficial velocities uL were 0.003-0.04m/s. The volumetric mass transfer coefficients kL. were correlated with the physical properties of liquid(Sc number), packing size, and flow conditions of gas and liquid, Three flow regimes obtained from the mass transfer study agreed with those obtained from fluid flow. The following correlations were obtained by regression analysis. Trickle-flow regime: Pulse-flow regime:
    On the Use of the Fast Fourier TransformAlgorithm for Studies on Liquid Backmixingin Three-Phase Fluidized Beds
    Hu Zongding and Zhao Xueming (Tianjin University)
    1985, 36(3):  347-355. 
    Abstract ( 501 )   PDF (455KB) ( 110 )  
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    Among all techniques for parameter estimation, the leastsquares analysis in the time domain is the most reliable, but the computational labor is often considered to be prohibitive. In this paper the authors have employed the FFT algorithm for the computation of the convolution integral, thus greatly shortening the computer time for parameter estimation. Liquid backmixing was investigated in a 92 mm I. D. threephase fluid-ized bed with the following conditions: gas velocity Ug 0.9-5.5cm/s, liquid velocity Ul 0.2 - 8.3cm/s. liquid kinematic viscosity r 0.81 - 39.6mm2/s, liquid surface tension a 39.7- 72.0mN/m and particle size 1.0- 1.25mm. Experimental results were correlated as follows: where Pe is the Peclet number. The mean deviation of the correlation is 15%.
    Synthesis Kinetics of Methyl Tertbutyl Ether
    Zhang Weike (Jilin Research Institute of chemical Technology)
    1985, 36(3):  356-365. 
    Abstract ( 644 )   PDF (510KB) ( 191 )  
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    Experiments proved that the etherification between methanol and iso-butene catalyzed by a macroporous sulfonic acid resin in producing methyl tertbutyj ether is a reversible reaction. At a certain temperature, there is a definite methanol/isobutene molal ratio (Rao), below which the etherification rate is second-order on isobutene concentration and negative first-order on rnethanol. When the ratio is higher than Rao, the reaction becomes first-order on isobutene concentration and zero-order on methanol. The dependence of Rao on temperature can be expressed as follows: The disether ification (reverse reaction) rate is first-order on MTBE concentration. The reaction rate equations may be given as when Ra is smaller than Rao, and when Ra is larger than Rao. The reaction is as taking place with the electrophilic mechanism. The solvated proton hypothesis suggested by other authors cannot explain the transition rates at methanol/isobutene ratio = Rao. A novel liquid-solid microreactor containing about 50 mg of catalyst was used in carrying out the experiments.
    Preparation of Birch Wood Holocellulose with Bromine and Dioxane
    Yu Huisheng and Chen Guofu (Tianjin University)
    1985, 36(3):  366-372. 
    Abstract ( 516 )   PDF (391KB) ( 94 )  
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    Holocellulose from birch wood can be prepared by the bromine method under proper conditions. The best bromination temperature is 20℃, and the time for bromination is five minutes per treatment. A monoethanolamine-1,4-dioxane solution provides a good solvent for the brominated birch lignin. A suitable concentration of monoethanolamine is 5%, and the proper temperature for extracting the brominated lignin is 70℃. The preparation of holocellulose from birch wood needs less repetitions of bromination and extraction than the chlorinedioxane method for the same Klason lignin and pentosan. Besides, both the equipment and operation are simpler for the bromine method.
    Analysis of Complete Pore Size Distribution for Active Carbon by Standard Isotherm
    Chen Songying (Shanxi Institute of Coal Chemistry, Academia Sinica, Taiyuan)
    1985, 36(3):  373-379. 
    Abstract ( 571 )   PDF (288KB) ( 269 )  
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    Two new methods for calculating pore size distribution, complete model-less method and modified micropore analysis method, have been developed. The complete pore size distributions of nine active carbons were calculated by the new methods. Nitrogen adsorption isotherms of nine samples were measured with Micromeritics 2500 Digsorb and ST-03 adsorption instrument. These isotherms were correlated by the Picketts equation and it was found that n values were in the range of 1.1-1.4. Since C values in Picketts equation were in the range of 100-300, standard isotherm n2 was chosen to analyze the complete pore size distribution. The main pore structure parameters, including total surface area, micropore area and volume, non-micropore surface area and volume and average micropore hydraulic radius, and the complete pore distributions of nine active carbon samples were obtained. Two ratios SR and VR were in the range of 0.9-1.1. The results indicated that samples Dx-09-1-1, 7S and J involved only micropore and the rest, including two active carbon fibers and four BPL active carbons, involved considerable amount of non-micropore.
    Removal of Guaiacol from Waste Water in Rotating Disc Columns
    Zhang Yuezhen and Shu Reshun (Shanghai Research Institute of Environment Protection)
    1985, 36(3):  380-384. 
    Abstract ( 477 )   PDF (263KB) ( 186 )  
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    The process of removing guaiacol from waste water has been studied in rotating disc columns with diameters of 73, 160 and 240mm. By investigating the effect of rotating speed, flow rates of waste water and emulsified liquid, amount of surfactant Span-80, it was found that the main factor affecting the removal of phenol is rotating speed, the optimal rotating speed decreasing with increase of column diameter. The rotating speed was correlated to the column diameter and to the minimal mass transfer unit height for the three column diameters.