Study On Mechanism And Model Of Gas-Liquid Mass Transfer Enhancement By Dispersed Particles

Gas-liquid mass transfer enhancement by dispersed particles is an important intensification method of chemical engineering process. This paper studies gas-liquid mass transfer enhancement mechanism and corresponding models.A united mechanism, including shuttle effect and hydrodynamic effect, has been proposed to develop 1, 2 or 3 dimensional single (or multi) point (or real) particle(s) models and a three-dimensional instationary heterogeneous irregularly-distributed numerous-particle di-mechanism (TIHIND) model.Gas absorption in blank solution simulation gives a reasonable computed unit cell of system (2Ï€DÏ„) and enhancement factor definition. In single (or multi) particle(s) models, the grazing or shuttle effect is applied as mass transfer enhancement mechanism. Using single (or multi) particle(s) models in this work, the effects of distance of particle to gas-liquid interface and partition coefficient between continuous liquid and dispersed particles on mass transfer enhancement are consistent with those in previous models. With a random particle distribution in computed unit cell, different total enhancement factors are obtained in multi particles models. Contribution ratio and screen coefficient of dispersed particles are introduced to study the inter-effect among particles in different models. Respect to 1-D and 2-D models, 3-D model gives the least screen coefficient, therefore TIHIND model is more reasonable.TIHIND model considers all enhancement factor contributions from all of particles in computed unit cell. The results show that (1) the random distribution of dispersed particles in computed unit cell is logical for about 5% average relative deviation; (2) E0 < 1 is possible in some cases; (3) the saturation effect of dispersed particles is reduced greatly due to numerous particles in computed unit cell. Therefore, the enhancement factor is high even for low partition coefficient; (4) the contact time and diffusion coefficient influence enhancement factor immonotonously; (5) the enhancement factor may have a peak value with increase of dispersed particles concentration; (6) gas and dispersed phase direct contact is possible; (7) the original solute concentration of solute will affect the mass transfer enhancement effect.TIHIND model is verified by the experimental data available in literature, theenhancement factors predicted from the model agree well with the experimental data. TIHIND model is more suitable than other previous models in (1) applicabilities for both dispersed solid-continuous liquid system and dispersed liquid-continuous liquid phase; (2) abilities of explaining enhancement factor change in a wide dispersed particle concentration; (3) prediction the enhancement factors change with time in experiment.According to the united mechanism proposed for TIHIND model, a general enhancement factor model (GEFM) is developed. By introducing a new concept of transient phase, GEFM can be used both in dispersed solid particles and dispersed liquid droplets systems. Respect to TIHIND model, GEFM has advantages of simple calculation and quick prediction of enhancement factor from a few experiments.Experiments of isobutylene and hydrogen absorption in water are carried out to verify the proposed mechanism and models.