A model for one-dimensional unsteady heterogeneous mass transfer was developed based on Danck-werts' surface renewal theory in order to describe the mass transfer enhancement of absorption process for a slightly soluble gas in a gas-liquid-liquid system.The model accounts for the mass transfer resistance within the dispersed phase and the effect of emulsion viscosity on mass transfer.An analytical solution for enhancement factor was obtained by Laplace domain transformation.The absorption rates of carbon dioxide in the dodecane-in-water and castor oil-in-water systems were measured in a thermostatic reactor,and the enhancement factors were calculated at different volume fractions of dispersed phase and stirrer speeds.The model predictions agree well with the experimental data.
There are still limited experimental data of liquid d if fusion coefficients in literature.Therefore, the experimental investigation and prediction model are of practical and theoretical significance.The diffusion coe fficients of L-serine, L-threonine,L-arginine,in aqueous solution at 298.15 K were measured respectively by holographic interferometer.The affecting factors of molecular structure and polarity were analyzed and discussed.Finally, a modi fied semi-empirical model for correlating the diffusion coefficients of solid o rganic compounds in aqueous solutions at 298.15 K was proposed with an adjustab le parameter added.The average deviation between model prediction values and exp erimental ones is less than 0.2%, which shows a considerably satisfactory accur acy.
A one-dimensional unsteady heterogeneous parallel mass transfer(ODUHPMT) model was developed for the absorption enhancement of volatile organic compounds(VOC) by the dispersed droplets.An analytical solution for enhancement factor was obtained based on surface renewal theory and the Laplace domain transformation. The absorption rate of propane into water at different stirring speeds with the added micro dodecane droplets was investigated experimentally in a thermostatic stirred tank.The mass transfer flux across the gas-liquid interface and the enhancement factor were measured.The results showed that the dodecane has an obvious enhancement effect on propane absorption into water,the maximum enhancement factor reached 11.The enhancement factor increased with increasing dodecane volume fraction and decreased with increasing stirring speed.The experiment data agreed well with the model predictions and showed high prediction accuracy of ODUHPMT model.
Two methods of the modification of zeolite were employed:framework element modification and surface coating,and the influence of the zeolites before and after modification on the CO2 absorption was investigated.It was found that although hydrophobicity of zeolite could be obtained by means of the surficial organic coating in the method of surface coating modification,partial channel of zeolite would be plugged,as a result,leading to the surface area reducing greatly.Distinctively,the framework element modification method could maintain not only complete lattice structure and adsorption capability of zeolite,but would also obtain a good hydrophobic property.Consequently,significant enhancement on gas absorption by this modified zeolite was achieved and up to a maxi-mum enhancement factor of 2.62.This shows that the solid particles with good enhancement role to gas absorption need not only good adsorptive capability but also certain hydrophobicity.An unsteady heterogeneous model was employed to predict enhancement factor and the calculated results agree well with the experimental data.
