ISSN:0001-1541    

DOI:10.1002/aic.690140402

出版商:American Institute of Chemical Engineers    

年代:1968

数据来源: WILEY

摘要:

AbstractThe dependence of extraction efficiency on flow distributions and droplet boundary‐layer behavior was investigated in a specially designed sieve‐tray extractor. Flow patterns and drop trajectories were obtained from residence‐time distributions and photographic observation. Extraction efficiency and continuous phase residence times were determined by a pulse technique.For most runs, flow behavior could be adequately described by the assumptions of perfect mixing in the continuous phase and plug flow of the drop phase. However, drop velocities were higher than predicted by single drop correlations, and the flow pattern was sensitive to minor changes in operating conditions. Observed extraction efficiencies were in good agreement with predictions based on observed flow patterns and the two film, surface stretch, mass transfer model of Angelo and Lightfoot. Approximately 90% of the stage mass transfer effectiveness appears to be due to the drop rise period, and essentially all the remainder to drop formation for the stage geometry selected.The greatest obstacle to reliable prediction of extractor performance is uncertainty as to the effect of operating conditions on flow distrib

ISSN:0001-1541    

DOI:10.1002/aic.690140403

出版商:American Institute of Chemical Engineers    

年代:1968

数据来源: WILEY

摘要:

AbstractThis paper reports a computational study of the evaporation rates of sprays of pure liquid drops having negligible velocity with respect to the air, and for drop velocities great enough to affect the evaporation rate. The principle parameters considered were the mean diameter and distribution of drop sizes in the initial spray, ratio of air to spray, initial temperature difference between air and spray, initial drop velocity, and air velocity.

ISSN:0001-1541    

DOI:10.1002/aic.690140404

出版商:American Institute of Chemical Engineers    

年代:1968

数据来源: WILEY

摘要:

AbstractIn many present day solids‐liquid contacting processes and slurry transport systems, the attrition rate of the solid particles is of primary technical and economic concern. Particle size degradation in a transport pipeline may make the delivered solids entirely unsatisfactory for the intended use, or separation of fines from the liquid phase and makeup of attrited solids may be so costly that an otherwise attractive process becomes unacceptable.Pilot scale tests to measure attrition in a slurry system are often costly and very time consuming. For this reason small scale tests have been developed for screening candidate systems prior to pragmatic pipe‐loop or pilot‐plant tests. Two of these test methods, crushing tests on individual particles, and annulus flow in a rotating cup apparatus, appear to give useful data on the relative attrition resistance of various solids and to provide a basis for estimating the attrition rate to be expected in a flowing system.Results obtained by using these test methods with silica gel in hexane and with molecular sieve particles in kerosene yielded some information as to the predominant mechanisms of attrition for these two types of solids. The brittle, glasslike silica gel appears to fail through impact fracture of small to medium size chips from the large particles, while attrition of molecular sieves results from surface abrasion, probably due to failure of the binder material, and yields only extremely fine products of attrition.This paper, which is based on a rather limited amount of preliminary experimentation, has been prepared in the hope that it may stimulate additional work on the development of useful standardized procedures for evaluating attrition resistance of s

ISSN:0001-1541    

DOI:10.1002/aic.690140405

出版商:American Institute of Chemical Engineers    

年代:1968

数据来源: WILEY

摘要:

AbstractLiapunov's direct method is extended to determine the stability of distributed systems with single and multiple equilibrium profiles. The method is simple to apply and makes use of certain inequalities to establish the sign definiteness of the time derivative of the Liapunov functional. Two numerical examples are presented, the adiabatic catalyst particle and an empty adiabatic tubular reactor with axial diffusion.

ISSN:0001-1541    

DOI:10.1002/aic.690140406

出版商:American Institute of Chemical Engineers    

年代:1968

数据来源: WILEY

摘要:

AbstractCalculation of fugacities of components in a gaseous or liquid solution directly from the corresponding states principle requires an improvement in the pseudo‐critical constants for the mixture. The derivation of the pseudo‐criticals must take into account deviations from the simple two parameter corresponding states principle which require additional parameters incorporated into the definition of the pseudo‐criticals. In this work parameters called molecular shape factors are introduced into the pseudo‐criticals. A generalized correlation for these shape factors is presented.Use of the shape factors greatly improves the calculation of vapor‐liquid equilibrium ratios for nonpolar hydrocarbon mixtures with large differences in molecular size and shape. Excellent results are obtained both in the low pressure and in the retrograde region when the pseudo‐reduced properties of the vapor and liquid lie within the range of accurately known properties of a reference fluid and the reduced temperatures for each component is greater than approx

ISSN:0001-1541    

DOI:10.1002/aic.690140407

出版商:American Institute of Chemical Engineers    

年代:1968

数据来源: WILEY

摘要:

AbstractNumerical solutions to the diffusion‐convection equations are obtained with a digital computer to establish the role of concentration level of the nondiffusing species in nonequivolume diffusion in fully developed turbulent flow of gases in pipes. Results indicate that under ordinary mass transfer rates for a system at constant Schmidt and Reynolds numbers product of the gas‐phase mass transfer coefficient and the log mean partial pressure of the nondiffusing gas is nearly constant both in the mass transfer entry region and in the fully developed region. These results are compared with the experimental data on vaporization and absorption processes.We show that the effect of the mass transfer section length on the rate of turbulent mass transfer is quite significant. Furthermore, the results of the diffusion—convection analysis are in better agreement with experimental data for sections of finite length than results calculated from the momentum‐mass transfer analogy. The two methods agree in the limit for tubes of infinite

ISSN:0001-1541    

DOI:10.1002/aic.690140408

出版商:American Institute of Chemical Engineers    

年代:1968

数据来源: WILEY

摘要:

AbstractThe stationary state hypothesis, commonly used for intermediates in complex kinetics in batch reactor studies, is analyzed in a tubular flow photoreactor. For practical values of the rate constants for the chosen kinetic sequence, it appears that the hypothesis is valid over all but a short entrance region of the reactor for both streamline and plug flow models. Even though the stationary state is quickly achieved, for the normal range of diffusivities, the conversion to product may be affected by radial diffusion and velocity profiles.In the course of the analysis the pertinent dimensionless parameters establishing the behavior of the reactor were identified. These arose from the differential equations expressing the conservation of radiant energy and mass in the system.

ISSN:0001-1541    

DOI:10.1002/aic.690140409

出版商:American Institute of Chemical Engineers    

年代:1968

数据来源: WILEY

摘要:

AbstractThe dynamic behavior of a packed liquid extraction column was investigated by comparing experimental frequency response data obtained from pulse testing with theoretical frequency response data. The theoretical model, which assumed that the column can be represented by a series of perfectly mixed cells, did not adequately describe the frequency response characteristics of the extraction process. However, by the utilization of various magnitude and phase correction factors, a technique was developed to obtain a semiempirical model that could be used to duplicate the actual performance of the liquid extraction column.

ISSN:0001-1541    

DOI:10.1002/aic.690140410

出版商:American Institute of Chemical Engineers    

年代:1968

数据来源: WILEY

摘要:

AbstractThe diffusion and mass transfer of a trace component in a background gas in a cylinder, is treated according to a relaxation transport equation. The system is assumed isothermal and at rest. An expression for an effective axial diffusivity is found which goes to the appropriate high and low density limits. Numerically, this diffusivity is similar to one half of the harmonic mean of the high density diffusivities, which is often used as an empirical extrapolating formula.The radial mass transfer problem results in an integral equation which is solved numerically for all Knudsen numbers.The case of catalytic reaction on the walls is considered in detail. Rarefaction effects become important under conditions of fast reaction. The problem of sublimation or evaporation from a cylinder wall can be treated by the same equations.

ISSN:0001-1541    

DOI:10.1002/aic.690140411

出版商:American Institute of Chemical Engineers    

年代:1968

数据来源: WILEY