Mass transfer coefficient

About: Mass transfer coefficient is a research topic. Over the lifetime, 7827 publications have been published within this topic receiving 168354 citations.

Mass Transfer of CO2 Into Water and Surfactant Solutions

Abstract: The mass transfer of CO2 into water and aqueous solutions of sodium dodecyl sulphate (SDS) is experimentally studied using a pressure, volume, temperature (PVT) cell at different initial pressures and a constant temperature (T = 25°C). It is observed that the transfer rate is initially much larger than expected from a diffusion process alone. The model equations describing the experiments are based on Fick's Law and Henry's Law. The experiments are interpreted in terms of two effective diffusion coefficients—one for the early-stages of the experiments and the other one for the later stages. The results show that at the early stages, the effective diffusion coefficients are one order of magnitude larger than the molecular diffusivity of CO2 in water. Nevertheless, in the later stages the extracted diffusion coefficients are close to literature values. It is asserted that at the early stages, density-driven natural convection enhances the mass transfer. A similar mass transfer enhancement was obser...

Volumetric mass transfer coefficients in slurry bubble columns operating in the churn-turbulent flow regime

Abstract: We report the results of an extensive experimental study of the gas hold-up, e, and volumetric mass transfer coefficient, kLa, in bubble columns operated at ambient temperature and pressure conditions. The superficial gas velocity U was varied in the range 0–0.4 m/s, spanning both the homogeneous and churn-turbulent flow regimes. Air was used as the gas phase in all cases. Three different measurement campaigns were carried out. In the first campaign the influence of liquid properties (viscosity, surface tension) were investigated in a column of 0.1 m diameter, equipped with a sieve plate distributor with 0.5 mm holes. Four different liquids were investigated: water, tetradecane, paraffin oil and Tellus oil, with viscosities ranging from 1 to 75 mPa s. The gas hold-up eG in these systems vary significantly. The volumetric mass transfer coefficient, kLa, closely follows the trend in gas hold-up. For the churn-turbulent regime of operation, i.e. U>0.08 m/s, the value of kLa/eG is found to be practically independent of U; the value of this parameter is found to depend on the liquid phase Schmidt number, showing a Sc−1/3 dependence. In the second campaign, we investigated the influence of catalyst particles addition (porous silica, mean diameter=38 μm) to the liquid phase (water and tetradecane), with slurry concentrations varying up to 25 vol.%. With increasing slurry concentrations, eG is significantly reduced due to enhanced bubble coalescence and for high slurry concentrations, the “small” bubbles are almost completely destroyed. For U>0.08 m/s, the value of kLa/eG is again found to be practically independent of U; this parameter is however significantly lowered with increased catalyst concentrations, due to increase in the size of the “large” bubbles. In the third campaign, the influence of increasing column diameter DT was investigated by experiments with water and Tellus oil. For both systems, kLa/eG shows a slight increase with DT in the churn-turbulent regime. This increase is due to increased liquid circulations with increasing scale, leading enhanced bubble split up. Our studies provide a simple method for estimation of kLa in industrial size slurry bubble columns operating in the churn-turbulent flow regime.

Organic cosolvent effects on sorption kinetics of hydrophobic organic chemicals by organoclays

Abstract: Data obtained from batch kinetics sorption experiments for naphthalene and diuron using two organoclays [trimethylphenylammonium (TMPA)-clay and benzyldimethyltetradecylammonium (BDTDA)-clay] in aqueous and methanol−water systems were analyzed with a first-order one-site mass transfer model (OSMTM) to obtain kinetic parameters. The mass transfer coefficient (e) exponentially decreased as the sorption coefficient (Kp) increased, and a log-linear increase in e was observed with an increase in the volume fraction of cosolvent (f c) in the system. Regression equations relating e to f c, measured in mixed solvents, could be extrapolated to f c = 0 to obtain the coefficients in aqueous systems. The organic cosolvent effects on the sorption kinetics behavior of naphthalene and diuron depended on the sorbate structure, the cosolvent fraction, and the arrange ment of the exchanged quaternary alkylammonium ions in montmorillonite-clay interlayers.