摘要:

AbstractA model is presented in which damaged pores are distributed throughout a network of undamaged pores within a spherical particle. The differential equations are solved according to the numerical procedure of Haynes, Jr. (1975). The model is intended to simulate more highly skewed chromatographic response curves than the two‐zone model recently proposed by Chou and Hegedus (1978).Pulse chromatographic measurements in fresh NaMgA zeolites using i‐butane as a tracer which only enters the macropores yield response curves with relatively low skew, which are readily fitted by a system of equations accounting for diffusion in a monodisperse pore system. For hydrothermally treated zeolites effective diffusivities and Henry constants are considerably lower and the skew higher than in fresh samples.Curve fitting with the model proposed below is quite satisfactory, and the characteristic parameters determined are approximately constant at the flowrates studied. Application of the model should not be restricted to hydrothermally treated zeolites, but may be extended to catalysts or adsorbents with macroporous structures damaged by other forms of age

ISSN:0001-1541    

DOI:10.1002/aic.690280202

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractAn analysis is presented to described the dynamics of fluidized bed adsorption columns. A microbial film model (recently proposed by the authors) is used to characterize the bacterial activity and its interaction with adsorption and solids mixing. Solids mixing and mixing in the liquid phase are included in the analysis, as is the effect of microbial film growth on the settling velocity of the adsorbent particles. The interplay of film growth, bed stratification and solids mixing is discussed in detail.

ISSN:0001-1541    

DOI:10.1002/aic.690280203

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractPrevious investigations of liquid‐to‐particle mass transfer in trickle beds have used non‐porous particles. However, the applications of trickle beds have been for reactions or adsorption employing porous catalysts as adsorbents. In this study a method of dynamic adsorption with porous particles is developed. The procedure is to extrapolate the response to a step‐function input of non‐volatile adsorbate to a short time where intraparticle diffusion and adsorption do not affect the overall process.The method is applied to the adsorption of benzaldehyde from aqueous solutions in a bed of granular, activated carbon particles. Measurements were made for three particle sizes, in adsorbers of two diameters, at 298K and 1 atm. The gas flow rate had no discernible effect on the mass transfer coefficients,kLsaLs, over a superficial velocity range of 1.47 to 8.0 × 10−2m/s, butkLsaLsincreased with liquid rate. The results, correlated as Sherwood vs. Reynolds number, agree well with the nonporous particle data of Van Krevelen and Krekels (1948), but suggest larger Sherwood numbers than similar data from later investigations.The wide range of mass transfer results for either liquid‐to‐particle or liquid‐to‐gas in trickle beds seems to be due in large measure to the difficulty in reproducing the rivulent flow pattern of li

ISSN:0001-1541    

DOI:10.1002/aic.690280204

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractThe mechanical power consumed in agitating aerated and nonaerated aqueous phases was measured and correlated using the data of previous investigators. The correlation is for a flat bladed turbine operating within the turbulent regime in fully baffled vessels. The accuracy of the predictions and the range of geometrical variations and equipment sizes support the use of the correlation for scaleup opreations.

ISSN:0001-1541    

DOI:10.1002/aic.690280205

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractA series of seven coals of different ranks and from various locations were heated in an inert atmosphere under relatively mild conditions to measure the rates of gas evaporation. Samples crushed to various fractions in the particle size range −6+50 U.S. mesh were studied at temperatures in the range of 150 to 300°C. The results show that: (1) most water is released at 100°C, evidently an evaporation process, (2) CO2is evolved at 150°C and above, and (3) CO is evolved at 250°C and above. An interpretive model was developed to fit the CO2production rate and kinetic constants were obtained. Gas evolution rates are independent of particle size for the most porous coals, but vary among coals, depending on both chemical composition and physical structure. A 15% loss in heating value was incurred during drying and subsequent oxidation when the pretreatment temperature was increased from 150 to

ISSN:0001-1541    

DOI:10.1002/aic.690280206

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractA model for packed‐bed reactors with dispersion is derived rigorously via the volume averaging approach. Though it is quantitatively more consistent with experimental data, it requires less computational efforts than the prevalent Fickian model. The adverse effects of dispersion on conversion are demonstrated both numerically and analytically using the new mode

ISSN:0001-1541    

DOI:10.1002/aic.690280207

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractAn investigation of photopolymerization in an isothermal and continuous stirred tank reactor (CSTR) was made. The existence of multiple steady states induced by gel effects was demonstrated theoretically and experimentally. This multiple steady state problem is presented in relation to reactor stability and control. Also, the relative behavior of the batch and CSTR systems is discussed.

ISSN:0001-1541    

DOI:10.1002/aic.690280208

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractA finite difference technique capable of simulating steady, incompressible, viscous, free‐surface flows has been successfully applied to the motion of a creeping Newtonian jet, including both surface tension and gravitational forces. In accordance with experimental results, the numerical solutions predict either a 12 or 16% increase in the jet dimensions depending on whether the jet emerges from a circular or a slit die. Both gravity and surface tension inhibit the swelling behavio

ISSN:0001-1541    

DOI:10.1002/aic.690280209

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractThe spherical cell model for transport in assemblages of spheres, which stems from the low Reynolds number hydrodynamics, has a serious physical limitation when extended to the range of intermediate Reynolds numbers. Spherical symmetry cannot persist around a sphere, given a definite direction of convection. The boundary conditions of the spherical cell model are inappropriate and a cubic cell model would best represent the system. However, in order to avoid undue mathematical difficulties peculiar to three‐dimensional problems, a cylindrical cell model is proposed.A numerical solution of the Navier‐Stokes equations expressed in vorticity‐stream function variables has been performed in conjunction with the cylindrical cell model for various values of porosity and Reynolds number. A much better agreement of the drag coefficient with experimental results is obtained by the cylindrical cell model than by the spherical cell

ISSN:0001-1541    

DOI:10.1002/aic.690280210

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY

摘要:

AbstractA simple technique is developed and is used to measure simultaneously the overall rate and the depth of the reaction zone in the porous solid. It is shown that by using some simple models, one may calculate the intrinsic rate constant and the pore diffusivity from the overall rate and the penetration depth. Models which allow for a varying pore diffusivity according to a linear porosity profile are presented, and have been shown more satisfactory than the constant diffusivity models of Thiele and of Zeldovich when applied to the high temperature carbon‐carbon dioxide reactio

ISSN:0001-1541    

DOI:10.1002/aic.690280211

出版商:American Institute of Chemical Engineers    

年代:1982

数据来源: WILEY