Numerical Simulation of Macroscopic Mixing in a Rushton Impeller Stirred Tank

The macroscopic mixing in a stirred tank with different tracer injection locations, impeller speeds and impeller positions is simulated numerically by solving the transport equation of the tracer based on the whole flow field in the baffled tank with a Rushton disk turbine numerically resolved using the improved inner-outer iterative procedure. Predicted mixing time is compared well with the literature correlations. The predicted residence time distribution of the stirred tank is very close to the present experimental results. The effect of the installation of a draft tube on the mixing time and residence time distributions is addressed.     

水溶性铑络合物催化1-十二碳烯氢甲酰化反应器构型的初步探索

Hydroformylation of 1-dodecene was studied in a biphasic system using water-soluble rhodium complex [RhCl(CO)(TPPTS)2] as catalyst in the presence of cetyl trimethyl ammonium bromide as surfactant to enhance the reaction rate. Efforts were devoted to improve the performance of hydroformylation by exploring reactor the reaction configuration which enhanced the mixing, dispersion and interphase mass transfer. Experiments were carried out in a 0.5L autoclave at the total pressure of 1.1MPa and temperature from 363K to 373K. Several surface aeration configurations were tested, and higher hydroformylation rate with higher normal/branched aldehyde ratio produced were achieved. The experience suggest that improved reactor configuration by taking reaction engineering, measures is beneficial to better process economy in alkene hydroformylation.     

权重积分方法计算界面张力消除表面“寄生”流

1 INTRODUCTION In simulation of multiphase flow in fixed Eule- rian grids by the level set approach and similar meth- ods, the accurate computation of surface tension force is critical. Two popular models were developed to model surface tension force: one is referred to as the continuum surface force (CSF) model[1―3] and the other is the continuum surface stress (CSS) model[4]. Both methods are commonly used for advecting inter- faces in the level set approach[5] and VOF (vol- ume-of-…     

Experimental and Numerical Investigations of Single Drop Mass Transfer in Solvent Extraction Systems with Resistance in Both Phases

Numerical simulation of transient mass transfer to a single drop controlled by the internal resistance or by the resistance in both phases was mathematically formulated and simulated in a boundary-fitted orthogonal coordinate system. The simulated results on the transient mass transfer dominated by the internal resistance are in good agreement with the Newman and Kronig-Brink models for drops with low Reynolds number. When the drop Reynolds number is up to 200, the mass transfer coefficient from numerical simulation is very low as compared with the Handlos-Baron model. The cases with mass transfer resistance residing in both the continuous and drop phases were simulated successfully and compared with the experimental data in three extraction systems recommended by European Confederation of Chemical Engineering (EFCE). For single drops with Re < 200, the numerically predicted values of the extraction fraction and overall mass transfer coefficient are in reasonable coincidence with the experimental data. I     

改善气液传质的新型表面曝气装置

A novel surface aeration configuration featured with a self-rotating and floating baffle (SRFB) and a Rushton disk turbine (DT) with a perforated disk has been developed. The SRFB, consisted of 12 fan blades twisted by an angle of 30° to the horizontal plane, is incorporated onto the impeller shaft to improve gas entrainment, bubble breakup, mixing in a φ154 mm agitated vessel. This new configuration is compared to the conventional DT surface aeration experimentally. The results suggest that the critical impeller speed for onset of gas entrainment is lower for the new configuration and it demands greater power consumption. Moreover, the SRFB system produces 30%-68% higher volumetric mass transfer coefficient per unit power input than that obtained in the conventional DT surface aerator under the same operation conditions.     

影响填料装填紧密程度因素的初步实验

散装填料装填的紧密程度影响填料塔的许多重要操作特性．本文在小型填料塔中进行简单的装填实验，考察了影响装填紧密程度的一些因素．结果表明，颗粒下落的终端速度和装填速率对填料装填紧密程度有明显的影响，较大的终端速度和较慢的装填速率有利于紧密装填．对长径比大于1的三叶形挤条，颗粒下落取向一致时装填密度较高     

用数值模拟方法分析混合和导流筒对搅拌槽中沉淀硫酸钡的影响

1 INTRODUCTION Precipitation of sparingly soluble salts is an im- portant operation widely adopted in the production of functional materials, catalyst, protein, pharmaceutical product and pigment. By precipitation, two aqueous streams containing respective reactants are mixed in a precipitator, and the sparingly soluble salt forms as result of chemical reaction if the concentration of produced salt exceeds its solubility. The quality of the final product obtained by precipitation is strong…     

RESIDENCE TIME DISTRIBUTION IN AN OPEN REACTOR:EFFECT OF BACKGROUND REACTANT ON TRACER DISPERSION

A new approach is presented for deriving the residence time distribution(RTD)in open-type reactors with exclusion of residence in the fore section.Inasmuch as failure to predict the con-version of chemical reactions has been evidenced in many occasions,numerical solution of tracerdispersion in the presence of background concentration gradient of reactant is given to demonstratethe strong effect of background reactant on the true RTD a reactant molecule experiences.Withinthe error of computation,the conversion of a first-order chemical reaction under steady state is shownto be equal in both closed and open reactors,despite difference in relevant RTDs     

Correlation between hysteresis of gas-liquid mass transfer and liquid distribution in a trickle bed

The hysteresis of gas-liquid mass transfer rate and the corresponding radial liquiddistribution in a trickle bed reactor are measured to provide evidence for the correlation between thesetwo behaviors.Experimental results indicate that the hysteresis of gas-liquid mass transfer originatesfrom the nonuniformity of the hydrodynamic state of gas-liquid flow and the radial maldistributionof local k_(gia) corresponds very well to the radial maldistribution of liquid flow in the bed.The localliquid flow rate is also found to be nonuniform in the azimuthal direction.In view of maldistributedliquid flow even in the pulsing flow regime,the conventional plug flow model seems oversimplifiedfor describing the behavior of a trickle bed.     

Experimental Investigation of Pressure Drop Hysteresis in a Cocurrent Gas–Liquid Upflow Packed Bed

Extensive experimental work on hysteresis in a cocurrent gas–liquid upflow packed bed was carried out with three kinds of packings and the air–water system. However, only when packed with small glass beads (f1.4 mm) was the bed pressure drop hysteresis observed. Two more liquids with different liquid properties were employed to further examine the influence of parameters on pressure drop hysteresis. The similarity of pressure drop hysteresis in packed beds was concluded in combination of experimental evidence reported in literature.