摘要:

AbstractTime‐averaged power dissipation rates have been measured in water in a 19.4 cm diameter reciprocating plate column operating at frequencies 0.6 to 3 Hz and amplitudes 5 to 20 mm. Measurements were also taken in water in a 15 cm diameter column operated at 1 to 5.7 Hz with amplitudes 1 to 10 mm. Several different types of doughnut reciprocating plates, fitting close to the column wall, were investigated. Power consumption at high amplitudes agreed with the predicted values using the quasi‐steady flow model, while at low amplitudes the data were more in agreement with a recently proposed acoustic model. The measured power dissipations were slightly affected by the spacing between adjacent plates, and by the alignment of the holes in the case of plates with 3 holes. Flow patterns around the reciprocating plates were also observed with the aid of a thin beam of light reflecting from small particles suspended in the liquid. Well‐developed circulation patterns were observed, depending strongly on the axial spacing between the p

ISSN:0008-4034    

DOI:10.1002/cjce.5450730401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe axial dispersion model has been commonly used to describe gas phase flow in bubble columns. Scatter in dispersion coefficients reported to date may be a result of the misuse of the axial dispersion model when a convective model would be more appropriate. Using simple tests with radioactive tracer response curve moments, convective and dispersive behaviours are differentiated. A convective model is presented. The model fits both tracer response curves and mean gas velocity well in both the bubbly and churn turbulent flow regimes, and may be used as a technique to calculate bubble rise velocity distributions.

ISSN:0008-4034    

DOI:10.1002/cjce.5450730402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractCe travail est consacré à la modélisation globale, à partir de la détermination expérimentale de la distribution des temps de séjour, de l'écoulement dans une cellule annulaire équipée de différents systèmes d'alimentation, pour des nombres de Reynolds compris entre 100 et 5000. En utilisant le modèle piston avec dispersion axiale, puis par l'association en série de réacteurs piston et parafaitement agité, nous montrons que l'écoulement tourbillonnaire non‐entretenu produit par une entrée tangentielle présente un caractère piston très prononcé, associé à une zone agitée due au système d'entrée‐sortie du fluide dans la cellule. L'utilisation d'une entrée axiale ou perpendiculaire à la cellule diminue le pourcentage du volume total du réacteur siège d'un écoulement piston par rapport à celui détermin

ISSN:0008-4034    

DOI:10.1002/cjce.5450730403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractHeat transfer coefficients to a liquid‐solid fluidized bed in a cylindrical tube have been measured using water as liquid phase and three types of cylindrical steel particles, as well as glass, nickel, copper and lead spheres of different sizes as solid phase. The independent varaibles included heat flux, liquid velocity and particle physical properties. The experimental results as well as a data bank containing a large number of measured heat transfer coefficients for solid‐liquid fluidization over a wide range of operational parameters have been compared with the predictions of most published correlations. A model for the prediction of heat transfer coefficients is proposed which predicts the present experimental data and the data of other investigators with good accur

ISSN:0008-4034    

DOI:10.1002/cjce.5450730404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA mathematical model is proposed to design condensers for vapor mixtures containing a non‐condensable gas. The Colburn and Drew (1937) film model is used, assuming the liquid flux to be completely mixed, but taking into account the interactions due to diffusion in the gaseous mixture. Some computational examples are given to show how the present model compares with the previous ones for the condensation of water‐methanol in the presence of air in a single tube condenser, and how the condensation of water‐ethanol mixtures in the presence of carbon dioxide in a shell‐and‐tube condenser evolves at different operating c

ISSN:0008-4034    

DOI:10.1002/cjce.5450730405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractMass transfer rates to and from drops in liquid‐liquid extraction equipment are often likely to be reduced by the presence of surface active contaminants. For industrial column design circumstances it is ideally required to account for the extent of contamination in a quantitative manner yet existing design procedures do not allow this to be done for the typical intermediate Reynolds number region of 10 to 100. A method is proposed for correcting continuous phase and drop mass transfer coefficients for the deleterious effects of contamination using only one contamination parameter which needs to be determined experimentall

ISSN:0008-4034    

DOI:10.1002/cjce.5450730406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIsoelectric precipitation of sunflower protein was carried out in a 10‐m long, 6‐mm internal diameter glass tubular precipitator. The effects of feed flow rate, protein concentration in the feed stream, and volumetric feed ratio of precipitant (HCl aqueous solution) to protein solution on solid protein recovery and particle size distribution were studied. The dispersion range of the tubular precipitator was modelled to predict the experimental results. Calculated initial growth rates of protein particles were found to: increase with increases in feed flow rate and protein concentration in the feed stream, and decrease with increases in volumetric feed ra

ISSN:0008-4034    

DOI:10.1002/cjce.5450730407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe catalytic conversion of canola oil to fuels and chemicals was studied over HZSM‐5, H‐mordenite, H‐Y, silicalite, aluminum‐pillared clay (AL‐PILC) and silica‐alumina catalysts in a fixed bed micro‐reactor. The reactor was operated at atmospheric pressure, a temperature range of 375−500°C and weight hourly space velocity (WHSV) of 1.8 and 3.6 h−1. An organic liquid product (OLP), light hydrocarbon gases and water were the major products. The objective was to maximize the amount of OLP and its hydrocarbon content as well as optimize the selectivity for gas phase olefinic hydrocarbons. In addition, the performance of each catalyst in terms of minimizing the coke formation was examined. Among the six catalysts, HZSM‐5 gave the highest amount of OLP of 63 mass% at 1.8 WHSV and 400°C. The hydrocarbon content of this OLP product was 83.8 mass%. With the exception of silica‐alumina and aluminum‐pillared clay catalysts, the other catalysts gave high concentrations of aromatic hydrocarbons which ranged between 23.1–95.6 mass% of OLP. The gas products consisted mostly C3and C4hydrocarbons. Ethylene, propylene and butanes were some of the valuable hydrocarbon gases. The olefin/paraffin ratio of the gas products was highest for AL‐PILC catalysts but it never exceeded unity. The results showed that it was possible to significantly alter the yield and selectivity for the different hydrocarbon products by using different catalysts or changing the catalyst functionality such as acidity, pore size and crystallinity. Reaction pathways based on these results are proposed fo

ISSN:0008-4034    

DOI:10.1002/cjce.5450730408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractLe test de microactivité (MAT), utilisé pour comparer les catalyseurs de craquage, fonctionne avec un réacteur approximativement piston, isotherme et non stationnaire. Les rendements à la sortie d'un tel réacteur sont calculés dans le cas d'un modèle cinétique à familles (lumps), d'une grande expansion molaire et d'une désactivation rapide du catalyseur fonction de la concentration en poison. Le poison (le coke dans le cas du craquage catalytique) est un produit résultant de plusieurs chemins réactionnels.Les résultats sont appliqués à la cinétique du craquage catalytique avec un modèle à 4 familles (charge, essence, gaz et coke).La comparaison entre les rendements observés et calculés, permet l'ajustement des constantes cinétiques à partir d'un groupe d'expériences réalisées dans des conditions variées.La simulation des profils de concentration dans le réacteur, permet une meilleure compréhension du

ISSN:0008-4034    

DOI:10.1002/cjce.5450730409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe times at which devolatilising coal particles fragmented were compared with their devolatilisation times in a fluidized bed combustor. Whereas the devolatilisation times were similar, the time to first fragmentation varied markedly from coal to coal. Immediate fragmentation was attributed to thermal shock. Fragmentation during the first 1/3 of the devolatilisation time was attributed to the internal pressure generated from restricted transport of volatiles through the pores in the coal structure. Fragmentation near the end of devolatilisation may occur due to weakening of the coal structure by loss of volatiles. Primary fragmentation did not affect the devolatilisation time, even for coals which fragmented early in their devolatilisation time.

ISSN:0008-4034    

DOI:10.1002/cjce.5450730410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY