摘要:

AbstractA method is presented to predict the shape of the gas‐particle interface between two plugs of cohesionless particles conveyed pneumatically through a horizontal pipeline. The method assumes that the moving solids are limiting equilibrium at the interface and that, therefore, the interfacial slope depends on the normal pressure gradient which can be used as a boundary condition for the numerical solution of Laplace's equation. The height of stationary material between the plugs cannot be predicted by the method, since this material is not in a state of limiting equilibrium. However, an analogy with a gas‐liquid system can be used to predict this height. The method as presented is restricted to plugs of constant voidage and to systems which obey Darcy's law (packed bed Reynolds numbers less than 10). The boundary element numerical technique is used to apply the method to a 2‐dimensional example of flow through a 50 mm I.D. pipe. The predictions are qualitatively in agreement with photographs of the observed shape in the true (3‐dimensional) situation. However, further numerical and experimental work on the 3‐D situation is required for a full assessment of the propos

ISSN:0008-4034    

DOI:10.1002/cjce.5450660201

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

年代:1988

数据来源: WILEY

摘要:

AbstractTwo phase flow in a horizontal pipe, with orifice plates placed at regular intervals as obstructions, was studied for the effect of phase velocities on flow patterns, fractional phase hold‐ups, pressure drop and liquid phase axial dispersion. Radioactive technetium‐99m (as an aqueous solution of sodium pertechnatate) was used as tracer. A pulse injection technique with two point measurements was employed. Three different orifice diameters were used (8 mm, 16 mm, and 20 mm) in a pipe diameter of 32 mm. The orifice spacing was 500 mm in all cases. Superficial gas (air) velocity was varied over a range from 0.02 m/s to 1.0 m/s and superficial liquid (water) velocity from 0.03 m/s to 0.85 m/s.Different flow patterns under different flow conditions were identified and a generalised flow map is presented. Variations in hold‐ups and pressure drop with flow patterns have been explained. Rational correlations have been developed for fractional phase hold‐ups and pressure drop. A preliminary comparison of two phase gas‐liquid flow in a horizontal pipe with orifice obstructions (to be called orifice pipe reactor), as a gas‐liquid contacting device, is made with a conventional bubble column reactor. Recommendations have been made for

ISSN:0008-4034    

DOI:10.1002/cjce.5450660202

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

年代:1988

数据来源: WILEY

摘要:

AbstractIn a series of two papers the results of investigating the mass transfer characteristics of two gas‐liquid reciprocating plate columns of the Karr type by different methods are presented. The subject of the first part is a study of the liquid phase volumetric mass transfer coefficient,kLa, while the second part deals with the interfacial area.The volumetric coefficientkLawas investigated using the sulphite method, the pure physical absorption of oxygen, and a dynamic method under culture conditions, the second of these three methods being the most favorable.Very good agreement among these methods was found. Generally,kLaincreased with increasing vibration intensity, superficial gas velocity, and the number of perforated plates. Liquid‐phase properties appeared to affectkLaonly slightly. The coefficientkLawas correlated in terms of the maximum power consumption and the superficial gas velocity:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_L a = 0.467 \cdot P_{G.m}^{0.25} \cdot U_G^{0.6} $$\end{docum

ISSN:0008-4034    

DOI:10.1002/cjce.5450660203

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

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper is the second part of a continuing study on mass transfer in a reciprocating plate column. The first part dealt withkLa. The bubble size distribution, the Sauter mean diameter and the interfacial area are the subject of this paper.The bubble size increases slightly with gas flow rate and decreases with agitation intensity above a “critical” level. The interfacial area increases with increasing agitation and aeration intensities, while the liquid flow rate and coalescing properties of the liquid have no significant effect. The specific interfacial area is correlated in terms of the superficial gas velocity and the maximum power consumption.The correlations obtained forkLaand a were used to calculatekL. It was found thatkLdepends on the agitation intensity and the bubble s

ISSN:0008-4034    

DOI:10.1002/cjce.5450660204

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe hydrodynamics of countercurrent air/water flow in a 5 cm diameter reciprocating plate bubble column have been studied; the plates contained 14 mm diameter perforations and had a fractional open area of 0.57. The ranges of superficial velocities of air and water were respectively 0‐0.99 cm/s and 0‐3.95 cm/s. The stroke was in most cases 4.5 cm and the reciprocation frequency was in the range 0–5 Hz.The pressure drops were measured in the absence of reciprocation for single phase and two phase flow conditions. Pressure fluctuations and time‐averaged pressure drops were measured with plate reciprocation under single and two‐phase conditions. The results were described in terms of the simple quasi‐steady state model; the effective orifice coefficients of the perforations were within the range 0.4 to 0.97 depending on the reciprocation conditions.The Sauter mean diameters of the bubbles decreased with agitation; they were about twice the values predicted from an earlier correlation developed for liquid‐liquid systems. The gas holdups were also substantially greater than predicted from correlations based on liquid‐liquid systems. Both these effects were explained as due to the tendency for bubbles to cluster in t

ISSN:0008-4034    

DOI:10.1002/cjce.5450660205

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

年代:1988

数据来源: WILEY

摘要:

AbstractOxygen absorption from air into water and axial dispersion in the aqueous phase have been measured in a 5 cm diameter reciprocating plate bubble column. The volumetric mass transfer coefficients in semi‐batch conditions were found to increase with agitation and were correlated with the specific power input and air flow rate. Under countercurrent conditions, it was found that axial mixing had little effect and conditions approached plug flow. The volumetric mass transfer coefficients were correlated with specific power input, air and water flow rates. Mass transfer coefficients were estimated using holdup and bubble diameter results. Comparison of the coefficients with the literature values indicated that the bubble surfaces were partially mobil

ISSN:0008-4034    

DOI:10.1002/cjce.5450660206

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

年代:1988

数据来源: WILEY

摘要:

AbstractDispersed phase holdup was measured in a pulsed plate column for the kerosene‐water system under binary conditions and under solute transfer from dispersed to continuous and continuous to dispersed phases. The experimental data were satisfactorily modelled through a recirculation regime model.The drop size distribution, measured by a photographic technique, exhibited a multinodal character at low agitation rates and high dispersed phase flow rate. Sauter mean drop diameter was found to depend on the agitation rate, the dispersed phase flow rate, the mass transfer direction and the plate free area. Correlations ford32and the interfacial area were presented using Kolmogoroff's isotropic turbulence mode

ISSN:0008-4034    

DOI:10.1002/cjce.5450660207

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

年代:1988

数据来源: WILEY

摘要:

AbstractDispersion coefficients were measured in a pilot‐plant sized agitated liquid‐liquid extraction column of the Kuhni type. Available techniques were considered, and the axial mixing in both phases obtained over a broad range of operating conditions, both with and without mass transfer and with two sets of stator plates. Earlier correlations for backmixing in the continuous phase were checked and improved, the final equation being successfully tested on available published d

ISSN:0008-4034    

DOI:10.1002/cjce.5450660208

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe solvent extraction of phosphoric, hydrochloric, sulphuric, hydrofluosilicic and hydrofluoric acids with long‐chain aliphatic amins is modelled. Pure acid equilibria are based on existing isotherms or calculated extraction constants when only experimental data are available. For binary mixtures binary combinations of acid complexes are added. In the aqueous phase Bromley's model for electrolytes is used for calculation of ionic activity coefficients and the appropriate association/dissociation equilibria taken into account for calculation of ionic strength. For the organic phase an empirical model for the non‐ideal behaviour of phosphoric acid is used. For multicomponent mixtures at low acid concentrations the model calculates the extraction of phosphoric, hydrochloric and sulphuric acid almost quantitatively. For hydrofluosilicic and hydrofluoric acid the calculations are less precise and further information is needed about the different fluoride exchange equilibria invol

ISSN:0008-4034    

DOI:10.1002/cjce.5450660209

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe effect of recycle on heat (and mass) transfer in concentric circular tubes has been investigated by finite difference methods. Theoretical results show that recycle can enhance the heat transfer rate for large Graetz numbers compared with that in an open tube (without an inner tube inserted and without recycle). Competition between a preheating effect and a residence‐time effect can be used to explain the heat transfer behavior. The heat transfer rate can be further augmented, with nearly no increase in total pressure drop, by employing flow pattern B instead of flow pattern

ISSN:0008-4034    

DOI:10.1002/cjce.5450660210

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

年代:1988

数据来源: WILEY