Influence of External Mass Transfer on Catalytic Reaction Rates on Metals

1977 ◽  
Vol 16 (3) ◽  
pp. 362-366 ◽  
Author(s):  
Daniel G. Löffler ◽  
Lanny D. Schmidt
Keyword(s):  
Mass Transfer ◽  
Catalytic Reaction ◽  
Reaction Rates ◽  
External Mass Transfer

STUDY OF EXTERNAL MASS TRANSFER DURING DRYING OF BERRY RAW MATERIALS TAKING INTO THE SHRINKAGE PHENOMENON

2019 ◽  
Author(s):  
А.В. АКУЛИЧ ◽  
Л.А. ГОСТИНЩИКОВА
Keyword(s):  
Mass Transfer ◽  
Energy Supply ◽  
Raw Materials ◽  
Mass Transfer Rate ◽  
Experimental Studies ◽  
Volume Shrinkage ◽  
External Mass Transfer ◽  
Transfer Coefficients ◽  
Ir Radiation ◽  
Criterial Equations

Исследованы закономерности внешнего массообмена при сушке ягодного сырья для различных способов энергоподвода. Установлено, что ягоды при сушке подвержены значительной объемной (72–81%) и линейной (35–43%) усадке, которую необходимо учитывать при расчете коэффициентов массоотдачи. Объекты исследования – ягоды черники, красной и черной смородины. Проведены экспериментальные исследования по сушке ягодного сырья при конвективном и конвективном с ИК-излучением способах энергоподвода. Исследования проведены при скорости сушильного агента хса1,2 м/с и температуре tса 70°С. Получены критериальные уравнения внешнего массоообмена при сушке ягод для периода постоянной скорости, учитывающие объемную усадку. Определено, что при сушке с конвективным энергоподводом объемная усадка при одном и том же значении критерия Рейнольдса оказывает на 12–20% большее влияние на интенсивность массоообмена для красной смородины по сравнению с черникой и черной смородиной. При сушке с конвективным энергоподводом, ИК-излучением и предварительным прокалыванием объемная усадка наиболее существенно влияет на массообмен для черной смородины, протекающий в 1,5–1,8 раза интенсивнее по сравнению с черникой и красной смородиной. Полученные критериальные уравнения могут быть использованы при расчете и проектировании установок для сушки ягодного сырья. The laws of external mass transfer during drying of berry raw materials for various methods of energy supply are investigated. It is established that the berries during drying are subject to significant volumetric (72–81%) and surface (35–43%) shrinkage, which must be taken into account when calculating the mass transfer coefficients. The objects of the study were various berries: blueberries, red and black currants. Experimental studies have been carried out on the drying of selected berries both in the case of convective and convective methods with IR radiation. Investigations were carried out at a drying agent velocity хса1,2 m/s and its temperature tca70°С. The criterion equations of external mass transfer during drying of berries for a period of constant speed, taking into account the volume shrinkage, are obtained. It was determined that during drying with convective energy supply, volume shrinkage with the same value of the Reynolds criterion on 12–20% has a greater effect on the mass transfer rate for red currants. When drying with convective energy supply, IR radiation and preliminary piercing, the volume shrinkage most significantly affects the mass transfer for black currants, which is 1,5–1,8 times more intense than blueberries and red currants. The obtained criterial equations can be used in the calculation and design of berries dryers.

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.

scholarly journals Pore Diffusion Model for the Adsorption of Basic Dyestuffs onto Natural Clay in Batch Adsorbers

1992 ◽  
Vol 9 (2) ◽  
pp. 109-120 ◽  
Author(s):  
Mohammad S. El-Geundi
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Diffusion Model ◽  
Sherwood Number ◽  
Pore Diffusion ◽  
Batch Adsorption ◽  
External Mass Transfer ◽  
Natural Clay ◽  
Pore Diffusion Model ◽  
Best Fit

The adsorption of basic dyestuffs (Basic Blue 69 and Basic Red 22) onto natural clay has been studied using a series of batch adsorption runs. The pore diffusion model (PDM) has been developed based on external mass transfer and pore diffusion to predict the performance of a batch adsorber. A computer program has been developed to generate theoretical Sherwood number-time curves and these results were adjusted to experimental Sherwood number-time curves by means of a ‘best fit’ approach. The variables of initial dye concentration and natural clay mass have been successfully correlated using a single external mass-transfer coefficient, Ks, and a single effective pore diffusion coefficient, Deff. The Ks values are 3.3 × 10−5 and 2.6 × 10−5 m/s for Basic Blue 69 and Basic Red 22, respectively. The Deff values are 7.3 × 10−10 and 9.6 × 10−10 m2/s for Basic Blue 69 and Basic Red 22, respectively.

scholarly journals Computational Approach for Ranking Mutant Enzymes According to Catalytic Reaction Rates

2009 ◽  
Vol 113 (11) ◽  
pp. 3579-3583 ◽  
Author(s):  
Malika Kumarasiri ◽  
Gregory A. Baker ◽  
Alexander V. Soudackov ◽  
Sharon Hammes-Schiffer
Keyword(s):  
Catalytic Reaction ◽  
Reaction Rates ◽  
Computational Approach

An algorithm for evaluating reaction rates of catalytic reaction networks with strong diffusion limitations

2001 ◽  
Vol 25 (9-10) ◽  
pp. 1185-1198 ◽  
Author(s):  
Sergio P. Bressa ◽  
Néstor J. Mariani ◽  
Néstor O. Ardiaca ◽  
Germán D. Mazza ◽  
Osvaldo M. Martı́nez ◽  
...  
Keyword(s):  
Catalytic Reaction ◽  
Reaction Rates ◽  
Reaction Networks ◽  
Diffusion Limitations ◽  
Strong Diffusion
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