摘要:

AbstractThe effect of cations on the gel strength of a bentonite clay was studied by measuring the maximum yield value of clay salt mixtures.Cations which are in large concentration as exchanged ions on the clay act very differently upon the clay strength than do cations which are only in trace concentrations in the clay. For those cations which were originally in only trace concentrations, the ability to build up the gel strength is inversely proportional to their valence.Sodium and calcium ions reacted completely differently. The clay was tolerant to a large sodium concentration but lost gel strength with the addition of only a small amount of calcium. This result is explained in the light of previously reported ion exchange properties of clay.

ISSN:0008-4034    

DOI:10.1002/cjce.5450520501

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

年代:1974

数据来源: WILEY

摘要:

AbstractA theoretical study of laminar natural convection over a semi‐infinite vertical plate is presented. The plate is of given, uniform concentration in some chemical species and convection is induced by diffusion into and chemical reaction with the ambient fluid. Steady state conditions are assumed. The equations used are basically those of the two‐dimensional boundary layer theory, modified to accommodate binary diffusion by Fick's second law, the Boussinesq approximation and homogeneous, irreversible isothermal reaction kinetics. A similarity transform to one variable is possible in the absence of chemical reaction; otherwise the problem is solved by perturbation expansions about an additional similarity variable which is dependent on the reaction rate. It is shown that the Schmidt number Sc and the reaction order n are the two fundamental parameters of the problem. Some analytical and numerical solutions are given for the ranges 10−2≤ Sc ≤ 104and 0 ≤ n ≤ 2. Calculations are presented in the form of graphs showing the concentration and flow fields within the convection layer. Generally it is found that the presence of chemical reaction expands the diffusion and velocity domains out from the plate, resulting in a larger, while less distinct, con

ISSN:0008-4034    

DOI:10.1002/cjce.5450520502

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe performance of inner‐fin and spirally indented heat exchanger tubes is compared with plain smooth tubes under severe scaling conditions. Artificially hardened water was recirculated through a heat exchanger which contained an enhanced tube and a plain tube in parallel and the decrease in heat transfer coefficient due to scale deposition followed with time. Inner‐fin and spirally indented tubes maintained advantages in heat transfer coefficient over plain tubes of 10 to 100% after scaling. Asymptotic fouling resistances were larger for the inner fin tubes than for plain tubes, and smaller for the spirally indented tubes at velocities above 3 ft/

ISSN:0008-4034    

DOI:10.1002/cjce.5450520503

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

年代:1974

数据来源: WILEY

摘要:

AbstractAxial dispersion in time‐variable laminar flow in a tubular reactor is analyzed using an exact procedure for the case of a homogenous first‐order reaction. For the first time since the Taylor Dispersion model was originally introduced for the modeling of reactors, its validity is examined over a wide range of the reaction rate parameter by comparison against anexact analysis.It is shown that a constant coefficient dispersion model can be obtained from first principles for large values of timeonly for initial distribution problems;however, this simple approximate model also is reasonably good for describing concentration distributions for the presentinlet distribution problemfor slow reactions and for axial locations sufficiently far away from the inlet. For rapid reactions, while the dispersion model is inaccurate in describing axial concentration distributions, it is surprisingly good for predicting the reactor length required for complete conversion. In contrast to the conclusion of a recent article, it will be shown that the dispersion coefficient isindependentof the reaction rate const

ISSN:0008-4034    

DOI:10.1002/cjce.5450520504

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

年代:1974

数据来源: WILEY

摘要:

AbstractTheoretical effects of parallel reversible chemical reactions on the rate of mass transfer are investigated in this paper. On the basis of the film theory, an analytical equation has been derived for gas absorption accompanied by first‐order parallel rversible reactions. Analytical approximate equations have been developed and finite difference techniques applied to study the enhancement of mass transfer by second‐order complex reactions. Results of this study indicate that when the diffusion is accompanied by second‐order parallel reactions, the mass transfer rate increases with the concentration of the liquid reactant in the bulk, and approaches that of diffusion and first‐order parallel reactions if the product of the diffusivity and bulk concentration of the liquid reactant is much larger than that of the gas r

ISSN:0008-4034    

DOI:10.1002/cjce.5450520505

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

年代:1974

数据来源: WILEY

摘要:

AbstractThis work studies the consequences of neglecting heat transfer effects in the Fick's law solution of food dehydration problems. A semi‐empirical approach is presented which correlates temperature and moisture changes of sugar beet root during the first falling rate period of drying; while the coupled heat and mass transfer equations are not solved rigorously, the approach gives a fairly accurate representation of the experimental results. An improved analysis through Fick's law is possible when the effect of changing sample temperature is considere

ISSN:0008-4034    

DOI:10.1002/cjce.5450520506

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe possibility of change in the algebraic sign of the net reaction rate of a single reversible reaction occurring in adiabatic or non‐adibatic batch and tubular reactors is investigated. This change is shown not to occur for adiabatic reactors; it may depending on the operating conditions and the system parameters for non‐adiabatic reactors. These and the related aspects of approach to system equilibrium are analyzed by an examination of the mathematical models describing these chemical reactors. Important results are summarized throughout the paper as Conclusions 1 ‐ 10. The results have direct applications in reactor design and operation. From a practical point of view it means that yield may be reduced in some cases by allowing too long a residence time even for a single reaction. Numerical examples are given to illustrate the re

ISSN:0008-4034    

DOI:10.1002/cjce.5450520507

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe kinetics of pseudocumene oxidation in the vapor phase with tin vanadate as catalyst have been studied over the following ranges of the variables: Oxygen concentration, 0.909 to 2.857 mole/m3; pseudocumene concentration, 0.071 to 0.125 mole/m3; temperature, 260 to 320°C; space time, 22.5 to 90 × 104g. catalyst/mole sec. Oxidation‐reduction models have been found to describe the kinetics adequately. The mechanism is found to remain the same throughout the temperature range cove

ISSN:0008-4034    

DOI:10.1002/cjce.5450520508

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe uncatalyzed oxidation of toluene and pseudocumene by sulfur dioxide has been studied at pressures ranging from 200 to 300 atm; and at tempratures from 250 to 350°C. It was found that under these conditions, toluene is readily oxidized and that the main oxidation product is benzoic acid. Pseudocumene, however, oxidizes to mono‐ and di‐carboxylic acids rather than to trimellitic acid. Power law rate equations are proposed for the two oxidations. Activation energy for toluene oxidation is estimated to be 47.6 Kcal/gm. mole while for pseudocumene oxidation the value is 71.2 Kcal/gm.

ISSN:0008-4034    

DOI:10.1002/cjce.5450520509

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

年代:1974

数据来源: WILEY

摘要:

AbstractTwo methods for measuring the rate constants of the elementary steps by the pulse technique are proposed. The first gives the adsorption and the desorption rate constants from the retention time and the half width of the chromatographic peak, and was applied to the adsorption of benzene on HY and CaY zeolites. The second gives the surface reaction rate constant and the desorption rate constant of the reactant from the peak of the product which is not adsorbed on the catalyst surface. The method was applied to the cracking of cumene on HY and CaY.

ISSN:0008-4034    

DOI:10.1002/cjce.5450520510

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

年代:1974

数据来源: WILEY