Optimal catalyst activity profiles in pellets. 2. The influence of external mass transfer resistance

1982 ◽  
Vol 21 (3) ◽  
pp. 284-289 ◽  
Author(s):  
Massimo Morbidelli ◽  
Arvind Varma
Keyword(s):  
Mass Transfer ◽  
Catalyst Activity ◽  
Mass Transfer Resistance ◽  
External Mass Transfer ◽  
Transfer Resistance

scholarly journals Modeling of the adsorption kinetics of zinc onto granular activated carbon and natural zeolite

2006 ◽  
Vol 71 (8-9) ◽  
pp. 957-967 ◽  
Author(s):  
Ljiljana Markovska ◽  
Vera Meshko ◽  
Mirko Marinkovski
Keyword(s):  
Mass Transfer ◽  
Activated Carbon ◽  
Simulation Study ◽  
Natural Zeolite ◽  
Granular Activated Carbon ◽  
Model Parameters ◽  
Mass Transfer Resistance ◽  
External Mass Transfer ◽  
Transfer Resistance ◽  
Kinetics Of

The isotherms and kinetics of zinc adsorption from aqueous solution onto granular activated carbon (GAC) and natural zeolite were studied using an agitated batch adsorber. The maximum adsorption capacities of GAC and natural zeolite towards zinc(II) from Langmuir adsorption isotherms were determined using experimental adsorption equilibrium data. The homogeneous solid diffusion model (HSD-model) combined with external mass transfer resistance was applied to fit the experimental kinetic data. The kinetics simulation study was performed using a computer program based on the proposed mathematical model and developed using gPROMS. As the two-mass transfer resistance approach was applied, two model parameters were fitted during the simulation study. External mass transfer and solid phase diffusion coefficients were obtained to predict the kinetic curves for varying initial Zn(II) concentration at constant agitation speed and constant adsorbent mass. For any particular Zn(II) - adsorbent system, k f was constant, except for the lowest initial concentration, while D s was found to increase with increasing initial Zn(II) concentration.

The Effect of External Mass Transfer Resistance during Drying of Fermented Sausage

2008 ◽  
Vol 26 (12) ◽  
pp. 1543-1551 ◽  
Author(s):  
İsmail Eren ◽  
Gülen Yıldız-Turp ◽  
Figen Kaymak-Ertekin ◽  
Meltem Serdaroğlu
Keyword(s):  
Mass Transfer ◽  
Mass Transfer Resistance ◽  
External Mass Transfer ◽  
Fermented Sausage ◽  
Transfer Resistance

Comparing biofilm models for a single species biofilm system

2004 ◽  
Vol 49 (11-12) ◽  
pp. 145-154 ◽  
Author(s):  
E. Morgenroth ◽  
H.J. Eberl ◽  
M.C.M. van Loosdrecht ◽  
D.R. Noguera ◽  
G.E. Pizarro ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Numerical Solutions ◽  
Heterotrophic Bacteria ◽  
Numerical Models ◽  
Single Species ◽  
Organic Substrate ◽  
Mass Transfer Resistance ◽  
Benchmark Problem ◽  
External Mass Transfer ◽  
Transfer Resistance

A benchmark problem was defined to evaluate the performance of different mathematical biofilm models. The biofilm consisted of heterotrophic bacteria degrading organic substrate and oxygen. Mathematical models tested ranged from simple analytical to multidimensional numerical models. For simple and more or less flat biofilms it was shown that analytical biofilm models provide very similar results compared to more complex numerical solutions. When considering a heterogeneous biofilm morphology it was shown that the effect of an increased external mass transfer resistance was much more significant compared to the effect of an increased surface area inside the biofilm.

Experimental determination of the dissolved oxygen boundary layer and mass transfer resistance near the fluid-biofilm interface

1994 ◽  
Vol 30 (11) ◽  
pp. 47-58 ◽  
Author(s):  
Tian C. Zhang ◽  
Paul L. Bishop
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Dissolved Oxygen ◽  
Boundary Layers ◽  
Mass Transfer Resistance ◽  
External Mass Transfer ◽  
Transfer Resistance ◽  
Concentration Boundary ◽  
Concentration Boundary Layers ◽  
Do Concentration

The thickness of the dissolved oxygen (DO) concentration boundary layer and the external mass transfer in a biofilm system were investigated using a microelectrode technique. Theoretical analysis was conducted to elucidate the mechanisms of the technique and to interpret the experimental measurements. The measured thicknesses of dissolved oxygen (DO) concentration boundary layers under different conditions demonstrated directly the effect of several factors on external mass transfer resistance. The experimental results indicated that (a) increasing substrate loading rate, (b) increasing fluid streamwise velocity and (c) increasing the roughness of the biofilm surface would decrease the external mass transfer resistance. The measured thickness of the DO concentration boundary layer was not in full agreement with theoretical correlations because the nonuniform biofilm created velocity and concentration fluctuations which resulted in the compression of concentration boundary layers. The microelectrode technique is a useful tool to study the external mass transfer resistance.

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