ISSN:0008-4034    

DOI:10.1002/cjce.5450700502

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

年代:1992

数据来源: WILEY

摘要:

AbstractA new technique was developed to determine the hydrodynamic characteristics of spouted beds. Under different operating conditions, this technique exploits the similarity of the voidage signals from different locations of the bed by means of coherence functions. The spout diameter as well as the minimum spouting velocity and maximum spoutable bed depth can be quantified by the values of the average coherence functions. The new approach presented in this paper is featured by its convenience and accuracy. It is eminently suitable for large size 3‐dimensional units which can not be visibly observe

ISSN:0008-4034    

DOI:10.1002/cjce.5450700503

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

年代:1992

数据来源: WILEY

摘要:

AbstractHydrodynamic parameters were investigated in a 0.15 m diameter half‐column spout‐fluidized bed at temperatures up to 880°C for ratios of auxiliary air flow to total air flow from 0 to 0.62 and four narrow size ranges of silica sand. Equations in the literature gave poor agreement with the minimum spouting velocity over the entire temperature range. For large particlesUmgenerally increased with temperature, while for small particles it decreased. Auxiliary air had more influence at elevated temperatures than at room temperature. Pulsations leading to choking appeared to cause spout termination at elevated temperatures. The McNab and Bridgwater (1977) equation correctly predicted the observed trends for maximum spoutable bed depth at high temperat

ISSN:0008-4034    

DOI:10.1002/cjce.5450700504

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

年代:1992

数据来源: WILEY

摘要:

AbstractHydrodynamic measurements were obtained in a half‐column of diameter 0.91 m equipped with a conical base using particles of diameter 3.3 to 6.7mm with operation both as pure spouted beds and in the spout‐fluid bed mode. Comparison of the experimental results for minimum spouting velocity with equations in the literature generally gave unsatisfactory agreement. On the other hand, the correlations of McNab (1972) and Hadžisdmajlović et al. (1983) gave reasonable predictions of spout diameters in spouted and spout‐fluid beds respectively. Hydrodynamic regimes with auxiliary air present were broadly similar to those determined in smaller columns. However, there were substantial dead regimes at the bottom of the column. A finite difference model based on the vector form of the Ergun equation gave good predictions of air flow distribution and longitudinal pressure p

ISSN:0008-4034    

DOI:10.1002/cjce.5450700505

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

年代:1992

数据来源: WILEY

摘要:

AbstractA multi‐dimensional model is developed to describe the fluid and particle dynamic behaviour of spouted beds. The position of the spout‐annulus interface is determined by a variational analysis. Two‐fluid equations are used to represent gas and solids motions in the spout while the vector Ergun equation and soil mechanics equations are employed to describe, respectively, gas and solids behaviour in the annulus. Using numerical finite difference methods, the set of governing equations is solved subject to carefully chosen boundary conditions. The model predictions of key hydrodynamic characteristics are in reasonable agreement with available measured data selected from the literature to represent a wide range of experimental condi

ISSN:0008-4034    

DOI:10.1002/cjce.5450700506

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

年代:1992

数据来源: WILEY

摘要:

AbstractOptimum conditions for the separation of added large particles from a spout‐fluid bed of Geldart Type B powder have been determined. A shallow bed, 100 mm in diameter, with porous conical distributor was used. Mean and distributions of residence time of the large particles depend on the two gas flow rates, especially that to the distributor, and on spout inlet diameter and large particle size. Bed regimes studied were mainly spouting with aeration and spout‐fluidization. In the latter regime an optimum range of fluidizing gas flow rates that minimised mean and spread of residence times was identified. RTD data were correlated by a model incorporating a minimum time supplemented by a distribution for an ideally mixed sys

ISSN:0008-4034    

DOI:10.1002/cjce.5450700507

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

年代:1992

数据来源: WILEY

摘要:

AbstractIn a liquid‐solid spouted bed system containing coarse and fine particles, the entrainment and elutriation of the separated fines were investigated with reference to variations in the pressure drop through the bed. The effect of operating parameters on the velocity corresponding to the beginning of entrainment of fines (Ube) was examined and a dimensionless correlation was proposed.The effect of operating parameters on the elutriation rate coefficient of fines at liquid velocities larger than their terminal settling velocity (Ul) also was studied. An empirical equation was proposed for a column height aboveTDH, the height of freeboard at which the elutriation rate becomes constant. It was recognized that the elutriation phenomenon was closely related to the length of the stratified particle transport bed when the ascending velocity of the elutriable particles at the top of bed becomes constan

ISSN:0008-4034    

DOI:10.1002/cjce.5450700508

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

年代:1992

数据来源: WILEY

摘要:

AbstractTwo slotted two‐dimensional spouted bed units with flexible bed dimensions were used with draft plates to study spouting pressure drop and minimum spouting superficial velocity. The data were collected while varying slant angle, spout width, separation distance, length of bed, height of bed, and size of bed (geometrical similarity) using shelled corn, soybean, and wheat. The variables which affect the spouting pressure drop and air flow through the beds are discussed. Empirical correlations are developed following the principles of dimensional analysis and similitude. The developed correlations agree closely with the collected dat

ISSN:0008-4034    

DOI:10.1002/cjce.5450700509

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe fluid flow pattern and solids circulation rate in a liquid phase spout‐fluid bed with a draft tube were studied in a semi‐circular column 196 mm in diameter equipped with a semi‐circular draft tube 34.5 mm in diameter using water and spherical glass particles 1.20, 1.94 and 2.98 mm in diameter. Both the solids circulation rate and fluid distribution between the draft tube and the annulus are influenced by the location of the draft tube, the relative magnitude of the inlet spouting and annulus flowrates, and the total fluid flowrate entering the bed.A one‐dimensional steady state model of vertical non‐accelerating liquid‐solids flow predicts the solids mass flux in the draft tube with a mean deviation of 12.3% when experimental values of the axial pressure gradients in the draft tube and annulus are specified. A simple correlation for the fountain height is als

ISSN:0008-4034    

DOI:10.1002/cjce.5450700510

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe development of a bed is reported, in which characteristics from spouted beds and pneumatic conveying are combined. The apparatus can be described as a pneumatic transport bed modified by the introduction of a recirculation process for inert materials, which leads to a final configuration akin to that of spouted beds. The dependency of the particle recirculation rates on the air flow rates and on the distance between the air inlet and the lower end of the central tube (z0) was investigated. Also studied was the variation of the total pressure drop with air flow rate, for different loads of inert materials (glass spheres,dp= 2.8 mm) and different z0values.

ISSN:0008-4034    

DOI:10.1002/cjce.5450700511

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

年代:1992

数据来源: WILEY