摘要:

AbstractA study was made of pneumatic transport of particles of sand suspended in air in a 31.8 mm diameter Plexiglas tube inclined at either 72 or 90 degrees with respect to the horizontal plane. The solids holdup, pressure gradient and pressure drop fluctuations over a 4.55 m test section were measured as functions of the air velocity and the solids flux. Previously observed sudden changes in slope of plots of solids holdup versus solids flux at constant gas velocity in a vertical tube (Mok et al., 1989), which were identified as transition points between dilute and dense phases, were confirmed and extended to inclined tubes. Breaks were also found in plots of pressure drop fluctuations versus solids flux at constant gas velocity.

ISSN:0008-4034    

DOI:10.1002/cjce.5450710202

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis work reports on bubble dynamics in polymer solutions of various rheological character. Relations between the friction factor and the Reynolds number are discussed and master curves based on the results of Kawase and Moo‐Young are presented and analyzed using two different viscosity expressions. The theoretical results overpredict the friction coefficient except at very high deformation rates. The surface tension is shown to affect the shape of the bubbles but not their velocity, except for bubble volumes smaller than 10‐

ISSN:0008-4034    

DOI:10.1002/cjce.5450710203

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

年代:1993

数据来源: WILEY

摘要:

AbstractA model of general application that is based on the definition of streamlines and that is in agreement with the bed geometry has been proposed in order to describe the gas flow in a jet spouted bed in conical contactors. The model quantifies the dispersion in the direction of the streamlines by using a characteristic modulus.The validity of the model has been experimentally proven on the basis of the measurement and analytical correlation of gas velocity profiles at different radial and longitudinal positions in the contactor, and of the application of the stimulus response technique for the calculation of the residence time distribution function.

ISSN:0008-4034    

DOI:10.1002/cjce.5450710204

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe power consumption and the volume‐based mass transfer coefficient (kla) for oxygen uptake from air into water have been measured for delta paddle impellers (10 cm and 20 cm diameter) in water in a 30 cm square sectioned baffled tank. Power consumption under ungassed conditions was measured in viscous mineral oil. For the 20 cm impeller, the effects of minor design modifications, such as sweeping the blade forward or back, have also been examined. The power numbers are approximately 2.0 in the absence of sparged gas, but are reduced by over 50% when gas is supplied beneath the impeller. Mass transfer data can be correlated with the power input per unit volume and the superficial gas velocity, showing that the performance with aeration of water is comparable to that reported by previous workers for the Rushton turbine impelle

ISSN:0008-4034    

DOI:10.1002/cjce.5450710205

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

年代:1993

数据来源: WILEY

摘要:

AbstractExtensive kinetic data for the methanation reaction over a Ni/Al2O3catalyst were obtained in a specially designed gradientless reactor operating at steady state. The reactor pressure was 101.3 kPa, and three temperatures were used, namely, 503, 513 and 523 K. The following three‐parameter phenomenological model based on a proposed Langmuir‐Hinshelwood mechanism adequately describes the data:r= L2K3K40.5k5P0.5H2Pco/ [1 +K3(k5/k6)Pco +K40.5P0.5H2]2With dissociative adsorption of hydrogen and hydrogen‐assisted dissociation of adsorbed carbon monoxide, the postulated mari is the CH surface group, and the rds is the hydrogenation of the surface CH

ISSN:0008-4034    

DOI:10.1002/cjce.5450710206

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

年代:1993

数据来源: WILEY

摘要:

AbstractLe présent article a pour objet ľétude théorique et expérimental des conditions thermiques et chimiques dans lesquelles s ' effectue la décomposition endothermique de particules solides sous ľaction ďun flux de chaleur extérieur. La réaction, du type Solide1→ Solide2+ Fluides est supposée s ' effectuer en régime chimique. Après une phase de chauffage pur, le grain solide commence à réagir dès q 'il atteint une certaine température seuilTR. La réaction s ' effectue alors dans des conditions quasi isothermes. Les variations deTRainsi que ľeffet de stabilisation de température dépendent des propriétés des particules, de la réaction chimique (cinétique et thermodynamique) et des conditions de transfert de chaleur, que ľon fait apparaǐtre sous forme de trois critères adimensionnels: critère ďactivation, de thermicité et nombre de Damköhler. Les prévisions théoriques sont en très bon accord avec les résultats de mesures expérimentales effectuées sur la réaction de déc

ISSN:0008-4034    

DOI:10.1002/cjce.5450710207

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

年代:1993

数据来源: WILEY

摘要:

AbstractExperimental results show that the electrochemical oxidation of oxalate in alkaline solutions at lead dioxide anodes can be achieved at conditions of much higher alkalinity than previously reported in the literature using other types of electrodes. The oxalate in solutions containing 0.05 mol/L ∽0.1 mol/L sodium oxalate was anodically oxidized to carbonate with high efficiency in the presence of up to ∽0.1 mol/L NaOH at 70°C by using lead dioxide anodes doped with silver and tin. The addition of small amounts of silver and tin (e.g., 0.06% by weight) to lead dioxide films significantly increases the oxalate oxidation currents and current efficiencies. These metals can be incorporated into the lead dioxide films by in situ oxidation of lead‐silver‐tin alloys. Although oxalate could not be electrochemically oxidized using lead dioxide electrodes at extremely high pH's (greater than ∽ 14), reduction of the oxalate concentration to less than about 0.04 mol/L could be achieved at greater than 50% current efficiency at pH's up t

ISSN:0008-4034    

DOI:10.1002/cjce.5450710208

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

年代:1993

数据来源: WILEY

摘要:

AbstractFractional gas holdup was measured in 0.57, 1.0, and 1.5 m i.d. vessels. Pitched blade downflow turbines (PTD) were used as the impeller. Design details of the impeller, such as the impeller diameter (0.22 T to 0.5 T) and blade width (0.25 D to 0.4 D), were studied. The effect of sparger type, geometry and size on fractional gas hold‐up has been investigated in detail. Four different types of spargers (pipe, conical, ring and concentric ring spargers) were used. Sparger location was varied for all the types studied. Further, design details of the ring sparger, which gave the highest hold‐up were then studied in detail. These included ring diameter, number of holes and hole size. All the reported correlations for fractional gas hold‐up in mechanically agitated gas‐liquid reactors were tested and compared. A better correlation has been developed for pitched blade t

ISSN:0008-4034    

DOI:10.1002/cjce.5450710209

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe heterogeneous phase transition of the organic vapours, cyclohexane and p‐xylene, on a cold substrate was observed by cooling the substrate at a slow rate under reduced pressure conditions. Either organic vapour at a vapour pressure lower than 130 Pa formed directly solid crystals but p‐xylene vapour at a higher vapour pressure formed liquid condensates with subsequent formation of solid crystals. The dependence of the critical supersaturation ratios on the critical temperatures and the physical properties of the organic vapours has been clarified by the equation derived on the basis of classical nucleation the

ISSN:0008-4034    

DOI:10.1002/cjce.5450710210

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe direct sulfation of three high purity limestones, all having more than 95% CaCO3but differing in petrographic texture, was studied in a thermogravimetric analyzer under simulated PFBC (Pressurized Fluidized‐Bed Combustion) conditions, that is, in the presence of enough CO2to prevent decomposition of CaCO3. Experiments were carried out over a wide range of particle size (53‐350 μm) at two temperatures (750 and 850°C), and two concentrations (1500 and 6000 mL/m3(ppmv) SO2). The particle size and temperature had a strong influence on the variation of the conversion with time. In contrast, the effect of concentration was rather marginal over the whole duration of the process, and the analysis of the initial reaction rate data gave a reaction order of 0.4, with respect to SO2, for all solids. The measured reaction rates were compared with those obtained in a past study for the sulfation of the calcines of the three solids under similar conditions. The initial rate of the calcine‐SO2reaction was found to be higher than that of the limestone‐SO2reaction, but since the former drops sharply as the pores at the external surface of the particles are filled with solid product, higher conversions may be obtained in some cases during direct sulfation for large react

ISSN:0008-4034    

DOI:10.1002/cjce.5450710211

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

年代:1993

数据来源: WILEY