Study On The Enhancement Mechanism Of The Gas Absorption Process By The Adsorptive Particles

The enhancement of gasliquid mass transfer is of central importance in theintensification of chemical engineering process. In this paper, the enhancementmechanism of gasliquid mass transfer with the dispersed particles was studied.The experimental investigations of carbon dioxide absorption in the slurriescontaining activated carbon and water had been carried out in the thermostaticreactor. The influence of particle concentration, stirrer speeds, ultrasonic dispersion,temperature and initial pressure on enhancement factor under the condition of theinitial pressure range from 101325pa to 162120pa, temperature varied between290.15K and 308.15K and stirrer speeds from 1 to 4 rounds per second had beeninvestigated experimentally. The results showed that the activated carbon had anobvious enhancement on carbon dioxide absorption in aqueous phase and its effectsdisplayed certain regulation that the enhancement factor notably increased duringbeginning period and consequently slowly raised to level off and gradually reached aconstant value with an increase of the solid loading within the range of zero to onekilogram per cubic meters. The enhancement factor reduced with increasing of thestirrer speeds. The system under ultrasonic dispersion appeared a remarkableenhancement comparing with the one without ultrasonic dispersion. Temperature hadlittle influence on enhancement factor while the initial pressure behaved a positiveact to the enhancement factor. All other kinds of particles used in this work had anegative effect on gas absorption rate.In view of the mass transfer happened near the interface, an one dimensionalnonsteadyheterogeneous mass transfer model was proposed according to thepartition of mass transfer region in which the shuttle effect mechanism and surfacerenewal theory were employed. An approach for enhancement factor had beenderived by means of Laplace domain transform and the influences of relativeparameters on enhancement factor were also discussed. The model presented couldbe applied to the prediction of enhancement factor in practical process.Due to the limitation of the classical theories in application range, a novelmodel based on interfacial nonequilibriummechanism had been proposed, and the absorption rate with and without the dispersed particles had been derived from thefundamental mass transfer equation, as well as the expression of enhancement factor.Considering the various ranges of stirrer speeds, different theories of mass transferled to different expressions of enhancement factor. Two different control regimes hadbeen put forward for the influence of the dispersed particles on enhancement factor:surfaceadsorption-control regime and surfacerenewal-control regime.In the two models mentioned above, one dimensional nonsteady heterogeneousmodel could well be applied to elucidate the relation between enhancement factorand solid loading as well as stirrer speeds under lower solid loading and stirrerspeeds, while the interfacial nonequilibrium model not only could be employed toexplain the relation above, but could also explain the relation between enhancementfactor and stirrer speeds under higher solid loading and higher stirrer speeds. Both ofthe two models could obtain the prediction equation of enhancement factorrespectively, and the predicted values agree well with the experimental data underthe condition of lower solid loading and stirrer speeds.