摘要:

AbstractThe height and structure of the fountain which forms in the freeboard region above the annular surface of a spouted bed is predicted based on equations of motion for particles entrained in the spout. Predicted fountain heights are in good agreement with a wide range of experimental values covering polystyrene particles, wheat, millet, glass beads and ammonium nitrate spouted in columns of diameter up to 0.292 m. A simplified procedure in which drag is ignored gives good results also under most circumstances of practical importance. The theoretical niodel proposed can be used to predict the voidage profile in the fountain core and the holdup of particles ill the freeboard, both of which may be useful in estimating the performance of spouted bed reactors.

ISSN:0008-4034    

DOI:10.1002/cjce.5450560501

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

年代:1978

数据来源: WILEY

摘要:

AbstractFor designing capsule pipeline systems the designer needs preferably simple mathematical models, to make quick calculations of the main characteristics of the system. For this purpose an easy to handle mathematical model for horizontal concentric capsule flow is proposed. In this model separate friction coefficients for the moving capsule wall and the pipe wall are introduced. These friction coefficients can be taken from the Moody chart. In the model only relatively long capsules are considered so that end effects can be neglected. The model gives expressions for the capsule velocity and the pressure difference across the capsule. Test results are in good agreement with the proposed model.

ISSN:0008-4034    

DOI:10.1002/cjce.5450560502

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

年代:1978

数据来源: WILEY

摘要:

AbstractWhen water was rotated by means of a “horse‐shoe” stirrer in a vertical, cylindrical tank and a stream was withdrawn from the bottom through a central exit pipe, a pronounced filament‐like vortex was formed under certain conditions. Experiments were performed to determine the factors which influenced the height of the vortex. The effects of vessel sue, stirrer geometry, rotational speed, exit flow rate and exit pipe diameter on vortex depth were studied. It was found that the vortex depth was highly dependent on the rotational speed, exit flow rate and exit pipe diameter. It was also found that under certain flow conditions the vortex penetrated the exit pipe. A relationship between the vortex depth and the pertinent variables was developed using dimensional analysis. The relationship resulting from a regression analysis of the dimensionless groups affecting the vortex depth was found to be:\documentclass{article}\pagestyle{empty}\begin{document}$$ H_v /d = 2.06\,(10^{ - 7})\,(\Omega d^3 /Q)^{0.71} \,(Q/vd)^{1.67} \,(D_2 /d)^{1.75} \,(H/d)^{0.60} $$\end{document}Motion picutes were taken showing the flow characteristics in the vicinity of the vortex by using a dye tracer technique. Ways of inhibiting vortex formation were also e

ISSN:0008-4034    

DOI:10.1002/cjce.5450560503

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe dispersion coefficient, the time delay and the time constant, as parameters associated with models of liquid phase axial dispersion in fluidized systems, have been correlated using available literature data for fluidization involving a wide range of fluid and particle properties. The results permit prediction of these parameters from only a knowledge of the bed voidage. A comparison with Chung and Wen's1correlation demonstrates the superiority of the present correlation.

ISSN:0008-4034    

DOI:10.1002/cjce.5450560504

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

年代:1978

数据来源: WILEY

摘要:

AbstractConditions are developed for the accurate measurement of mass transfer coefficients, internal diffusivity and adsorption rate constants using pulse gas chromatography within the limits of the approximation of the Kubin‐Kucera model for adsorption in a packed bed. Physisorption rates are shown to be many orders of magnitude higher than those measurable. Thus, pulse chromatography cannot be used to determine physisorption rate constants. Mass transfer coefficients at low Reynolds Numbers are shown to be measurable under severely restricted condition

ISSN:0008-4034    

DOI:10.1002/cjce.5450560505

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe extended crossflow model was proposed earlier5to account for the role of the stagnant zones of liquid in a packed trickle bed during absorption with a chemical reaction. Here the model is applied to a second order reaction to investigate the behaviour of the effectiveness f of the interfacial area of the static hold‐up during absorption with a chemical reaction. General criteria are developed which give conditions for the limiting behaviour of f for reaction kinetics of any form. Finally, a possible pitfall is described in detail which must be avoided in conducting kinetic experiments in a packed trickle be

ISSN:0008-4034    

DOI:10.1002/cjce.5450560506

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe hydration of acetic anhydride in concentrated solutions has been studied in a vertical laminar flow reactor. The effects of flowrate, reactant concentration and reaction conditions on conversions and temperature rises were studied. An effect of the initial acetic acid concentration was observed. Thus at low acid concentrations there was good agreement between experimental and prediction values. However, at high acid concentrations, above 1.2 mole/l acid, the reaction was apparently inhibited and experimental results were lower than predicted. Radial teniperatnre profiles were measured and found to be relatively flat despite the low Reynolds numbers existing iu the reactor.

ISSN:0008-4034    

DOI:10.1002/cjce.5450560507

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

年代:1978

数据来源: WILEY

摘要:

AbstractReaction between cupric oxide, oxygen, and sulphur dioxide has been studied in a fluidized bed reactor continuously fed with solid reactant. The effect of bed temperature, solid flow rate, gas flow rate and the hight at minimum fluidization conditions has been investigated.Experimental conversions are between 20 to 60%.Olcutt and Davidson's fluidized bed reactor model slightly modified for our particular reactor has been compared with experimental data. The assumption of plug flow of gas in the dense phase is good for the height of 5 cm, on the contrary, the assumption of perfect mixing of gas in the dense phase is better for the deepest bed.

ISSN:0008-4034    

DOI:10.1002/cjce.5450560508

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe methanation of carbon monoxide was studied over various supported nickel catalysts in a fixed bed reactor in the temperature range of 250 to 400°C. The hydrogen to carbon monoxide ratio was kept higher than stoichiometric in order to avoid carbon formation. The catalyst particles had an average diameter of 80 pm and nickel contents ranging from 5 to 42 wt %. The performance of laboratory prepared catalysts was compared with commercial ones. The catalysts were characterized by BET surface area, pore volume and carbon monoxide chemisorption. Specific activities for the methanation reaction were obtained and were found to vary with nickel concentration and with crystallite size. There exists a crystallite size range in which the maximum activity was observed. Metal support interactions may also contribute to the vdation in specific activity. The activation energy was found to vary from 58.2 MJ/kmol to 119.4 MJ/kmol. It appears that the methanation reaction over Ni/aIumina catalysts is a structure sensitive reaction. A compensation effect was observed for this reaction

ISSN:0008-4034    

DOI:10.1002/cjce.5450560509

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe problem of multicomponent gas phase diffusion fora single overall reaction in porous catalysts is analyzed using the dusty‐gas theory. Recent authors have shown that neglecting internal pressure gradients results in modeling inconsistencies and errors in computation in small pore catalysts. However, calculations based upon kinetic theory estimates of the transport coefficients reveal that the viscous flow contribution to the component i molar flux can be neglected with excellent justification. The resulting equations are internally consistent and greatly simplified. For illustrative purposes the multicomponent example of P. Schneider7is reformulated to take into account nonuniform pressure (but negligible viscous flux), and as a consequence the inconsistency noted in the original reference is removed. Two methods for computing the effectiveness factor are discusse

ISSN:0008-4034    

DOI:10.1002/cjce.5450560510

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

年代:1978

数据来源: WILEY