摘要:

AbstractParametric sensitivity of tubular reactors is analyzed to provide critical values of the heat of reaction and heat transfer parameters defining runaway and stable operations for all positive‐order exothermic reactions with finite activation energies, and for all reactor inlet temperatures. Evaluation of the critical values does not involve any trial and erro

ISSN:0001-1541    

DOI:10.1002/aic.690280502

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractExperimental results for instantaneous and time‐averaged local heat transfer coefficients, as well as local voidage and pressure are used to validate the Adams‐Welty analytical model of heat transfer to a horizontal cylinder in large‐particle fluidized beds. Results support the main assumptions of the model and show that the range of applicability is wider than originally exp

ISSN:0001-1541    

DOI:10.1002/aic.690280503

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractFor a catalyst composed of a more active component embedded in a less active (but not inert) and more diffuse matrix, an optimum distribution of the active component in the catalyst pellet may lead to significantly higher reaction rates per unit volume of pellet, compared with reaction rates using pellets with a uniformly distributed active component or with an active component concentrated on the outside or the inside of the pellet. The optimum distribution changes qualitatively with the physical parameters of the pellet and with changes in the rate constants and diffusion coefficients of the catalytic compoenents. This is relevant to the performance of coking zeolite/silica‐alumina catalysts in hydrocarbon cracking reaction

ISSN:0001-1541    

DOI:10.1002/aic.690280504

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractCrystallization kinetics of sodium chloride have been studied in a Continuous Mixed Suspension Mixed Product Removal evaporative crystallizer at 50°C. A marine propeller was found to give a substantially lower nucleation rate than a pitched blade impeller under identical conditions. The crystal turnover time did not affect the effective nucleation rate

ISSN:0001-1541    

DOI:10.1002/aic.690280505

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractThe kinetics of the thermal regeneration of activated carbons used in the waste water treatment was analyzed on the basis of a model that the regeneration reaction consists of a set of many first‐order reactions each of which has different activation energy and frequency factor. The frequency factors were correlated approximately by a function of the activation energy.The difference in the activation energy was represented by a distribution curve which was obtained by analyzing the thermogravimetric curve (TG curve) measured under a constant heating rate. The weight loss during the regeneration reaction under complicated heating conditions was well predicted by use of the distribution curve determined by the proposed method. This method describing the kinetics of the thermal regeneration may be applied to the design of reactors regenerating spent carbon

ISSN:0001-1541    

DOI:10.1002/aic.690280506

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractThe transport in composite media obtained by dispersing a porous active catalyst inside an inert porous medium has been considered here. Since such systems show a wide variety of advantages, it is necessary to obtain the correct transport equations. Very dilute systems are considered (volume fraction of catalysts ≪ 1/3), a condition that any one dispersed catalyst microsphere cannot feel the influence of others arises. An averaged conservation equation at steady state is obtained under the above condition as well as the condition that any one microsphere can be randomly placed in the medium. Similarly, an effective diffusion coefficient has been obtained.The results differ from the ones previously in use. The enhancement in the reaction rate on diluting a catalyst is seen to be much less than the values previously suggested although a qualitative similarity exist

ISSN:0001-1541    

DOI:10.1002/aic.690280507

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractAn experimental and theoretical study was carried out to relate the extent of channeling in a packed column to the response in the effluent gas to a tracer input. When the response curve showed a distinct peak associated with a channel, it was possible to establish the flow rate and void area of the channel from only the response curve. The experimental data provided new information on Peclet numbers in packed columns with nonuniform void fractions (low tube‐to‐particle diameter rati

ISSN:0001-1541    

DOI:10.1002/aic.690280508

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractOverall heat transfer coefficients were measured for an instrumented horizontal tube of diameter 25 mm in the feedboard region above fluidized beds of 102 μm, 470 μm and 890 μm sand in a 0.25 m × 0.43 m × 3.0 m tall pilot scale column. The superficial air velocity varied from near minimum fluidization to 1.7 m/s. The instrumented tube was placed at different positions in a 16‐tube bundle. The measured heat transfer coefficients were bounded for tubes near the expanded bed surface by the immersed tube values, and for remote tubes by the values for particle‐free air in crossflow. The results are correlated within ± 12% by a simple equation which incorporates these limits. The results are in good qualitative and quantitative agreement with previous experimenta

ISSN:0001-1541    

DOI:10.1002/aic.690280509

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractA generalized mathematical model is developed to describe the process of multicomponent adsorption on activated carbon in fixed beds. Numerical, finite difference, solutions for the adsorption of binary, and ternary organic mixtures are shown to satisfactorily match previously published experimental data.

ISSN:0001-1541    

DOI:10.1002/aic.690280510

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractA relatively simple and extremely versatile optical method of obtaining diffusion coefficient data known as Gouy interferometry was employed to measure diffusion coefficients in undersaturated and supersaturated aqueous urea solutions at 25°C. The use of laser light as a monochromatic light source in the interferometer greatly simplified the procedure for obtaining diffusivity data from the interferometer. A novel design of a real image camera was employed to record the interferometric data. Values obtained from the interferometric data for low concentration (0–4 molar) aqueous urea solutions were within ±5% of literature values.The diffusion coefficient was found to decrease linearly with increasing concentration up to the saturation point of the aqueous urea solutions, and to decrease drastically with increasing concentration in the supersaturated region. This behavior is similar to that observed in liquid‐liquid systems near the consolute point (Cussler, 1980). It is speculated that this phenomenon is a result of molecular aggregation of the urea molecules in supersaturated aqueous solutions. Very little experimental data have previously been obtained in the supersaturated region due to crystallization problems. Supersaturated diffusion coefficient data are important in the study and design of crystallization processes.The solid‐solute‐liquid solvent binary systems urea‐water and sucrose‐water were modeled as a saturated solution solute‐liquid solvent system in order to test various concentration dependent diffusion relationships. Two of these relationships, the Vignes and Leffler‐Cullinan equations, showed improved correlation with experimentally determined diffusivity data for aqueous urea and aqueous sucrose solutions at undersat

ISSN:0001-1541    

DOI:10.1002/aic.690280511

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY