摘要:

AbstractInduction phenomena are explained that exist in the only two reproducible sets of kinetic data in the literature for gas hydrate formation from an agitated ice surface. The previously unexplained data are interpreted using recent crystal diffraction results. The induction explanation is validated through cyclopropane hydrate kinetic experiments. The induction reasoning forms the basis of an hypothesis for a molecular mechanism of hydrate formation from ice. The hypothesized mechanism is quantified and given physical interpretation. The hypothesis may have significant implications for inhibiting hydrate formation.

ISSN:0001-1541    

DOI:10.1002/aic.690370902

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractA method to evaluate nucleation and crystal growth rates from batch cooling crystallization experiments is presented. Solute concentration and suspension temperature are recorded during the experiment and the product crystal size distribution is analyzed. The crystal growth and nucleation rates at any instant are calculated by solving the population balance equation using the method of characteristics, together with the mass balance equation. Based on a set of different cooling crystallization experiments, kinetics for succinic acid are determined. Applying these kinetics in process simulation allows for a reasonably accurate prediction of the product weight mean size.

ISSN:0001-1541    

DOI:10.1002/aic.690370903

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThe problem of freely‐suspended liquid droplets deforming due to an applied electrostatic field is examined. Developed is a numerical model capable of predicting the complete transient histories of droplets in systems with a wide range of dispersedand continuous‐phase densities, viscosities, relative permittivities, and electric field strengths. For liquid/gas systems, the predictions of the numerical model demonstrated that the critical field strength and critical permittivity ratio during actual transient breakup are not necessarily the same as those predicted by steady‐state theories. An approximate analytical model of transient droplet deformation is also developed, which is able to predict the deformation time histories for large Ohnesorge number, small‐deformation liquid/liquid systems. The approximate analytical model agreed well with the results of the complete numerica

ISSN:0001-1541    

DOI:10.1002/aic.690370904

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractA flexible and structured methodology for the computer‐aided molecular design (CAMD) by the group contribution approach is presented. The proposed CAMD algorithm takes the following four steps: 1. preselect groups and target properties; 2. generate only a feasible set of compound structures in an optimal fashion; 3. predict properties for the screening of the set of feasible compound structures; and finally 4. select/design the compound. Since the success of any CAMD algorithm depends to a large extent on its ability to predict/compute the needed properties, the importance of the choice and applicability of these methods is considered along with the computational aspects related to the development of a computer program based on the proposed methodology. Finally, the scope of CAMD technology is highlighted using several practical example

ISSN:0001-1541    

DOI:10.1002/aic.690370905

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractIn chromatographic separations involving elutes with large differences in the molecular size, the adsorption saturation capacities of the elutes may differ because of the differences in the degree of size exclusion. With uneven saturation capacities, isotherm crossovers may occur, which often results in selectivity reversal. In this work, a new multicomponent isotherm has been developed for this kind of system. The isotherm is an extension of the common multicomponent Langmuir isotherm and introduces no or a very limited number of new parameters for its construction. The isotherm crossover conditions have also been derived. Simulations based on a general rate model using the new isotherm have successfully demonstrated the phenomena of peak reversal and crossover of breakthrough curves.

ISSN:0001-1541    

DOI:10.1002/aic.690370906

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractWe present an explicit analytical solution for the Lévêque's problem with the boundary condition of the third kind. This solution is applicable to problems of mass (heat) transfer with surface reaction (surface resistance) in the entry region of fully developed flow fields of power law fluids, and to the developing boundary layer flows that admit Falkner‐Skan solutions, provided that the Schmidt (Prandtl) number is large. The series form of the solution developed by inversion of the Laplace transform has excellent convergence properties within the concentration (temperature) boundary layer in contrast to the integral forms that are usually reported for problems of this type. An efficient computational algorithm for evaluation of the surface concentration is presented, as well as accurate approximate formulas in the form of simple algebraic expressions for the local and average mass (heat) transfer coefficients and the surface concentration (temperatu

ISSN:0001-1541    

DOI:10.1002/aic.690370907

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractA new steam cracking technology has been developed that uses honeycomb‐type ceramic reactors with high surface to volume ratios and is heated by flue gas. “Rectangular” process gas temperature profiles are possible with such a reactor. An optimal combination of temperature profile and residence time leads to a very significant increase in olefins yield with respect to conventional cracking units. Benchscale results are compared with predictions based on a reactor model, which accounts in great detail for the geometry of the structure and the associated heat transfer, combined with a rigorous kinetic model based on radical reaction mecha

ISSN:0001-1541    

DOI:10.1002/aic.690370908

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractA mathematical model is developed to describe the dynamic and pseudosteadystate behavior of chemical vapor infiltration, a process used to fabricate fiber‐reinforced ceramic matrix composites. The three‐parameter dusty‐gas model is used to describe the interaction of mass transport fluxes, partial pressures, and partial pressure gradients in the interior of the porous medium, with the viscous flux related to the total pressure gradient through Darcy's law. The model is applied to study the deposition of SiC via decomposition of methyltrichlorosilane in a porous medium whose structure can be represented by a population of uniformly‐sized, randomly‐overlapping pores. The results show that use of simplified mass transport flux models can lead to significantly different results, even if the concentration of reactants is low and the effects of the products of the reaction on the deposition rate are ignored. It is also shown that operation of chemical vapor infiltration reactors under pressure pulsing can lead to conversion gradients in the densifying structure by a few orders of magnitude smaller than those seen at the same reaction conditions under constant

ISSN:0001-1541    

DOI:10.1002/aic.690370909

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractAn accurate, yet simple, equation of state was developed for pure fluids ranging from nonpolar to H2O and their mixtures. The equation consists of a virial expansion truncated after the fourth virial coefficient and a closed‐form term approximating higher coefficients. For nonpolar or weakly polar compounds, the equation is generalized using critical temperature, critical pressure, and acentric factor. Despite its simplicity, the equation represents the P‐V‐T and saturation properties of pure fluids with a very good accuracy, which is comparable to that of multiparameter, generalized BWR‐type equations. For mixture calculations, mixing rules were formulated based on the rigorously known composition dependence of virial coefficients. The equation represents vapor‐liquid, gas‐gas and liquid‐liquid equilibria, as well as volumetric properties of mixtures containing nonpolar components and/or water. Binary parameters can be generalized for series of mixtures containing a com

ISSN:0001-1541    

DOI:10.1002/aic.690370910

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractBaffle effects on the performance of a catalytic circulating fluidized bed reactor were examined experimentally. The circulating fluidized bed reactor or riser was 102 mm in diameter and 6.32 m in height. Reaction was the catalytic decomposition of ozone using FCC particles with a mean diameter of 89 μm, impregnated with ferric oxide as catalysts. Four ring‐type baffles, mounted horizontally around the riser wall, were used in this study. Ozone concentrations were measured in both axial and radial directions under various operating conditions in a riser with and without baffles. Experimental results showed that in a riser with baffles, the ozone concentration in the radial direction was more uniform and the ozone conversion was higher than that in a riser without baffles except at the lowest gas velocity used. A mathematical model developed accounted for the gas‐phase ozone conversion under various operating conditions. The gas‐solid contact efficiency in the riser was discussed in light of the

ISSN:0001-1541    

DOI:10.1002/aic.690370911

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY