Particle−Liquid Mass Transfer Coefficient in Two-/Three-Phase Stirred Tank Reactors

AbstractThe results of studies concerning two- and three-phase systems in an agitated vessel are presented. The aim of our research was to investigate the effect of the physical properties of the liquid phase on the value of the volumetric gas-liquid mass transfer coefficient in mechanically agitated gas-liquid and gas-solid-liquid systems. Our experimental studies were conducted in a vessel with an internal diameter of 0.288 m. The flat bottom vessel, equipped with four baffles, was filled with liquid up to a height equal to the inner diameter. The liquid volume was 0.02 m3. Three high-speed impellers of a diameter equal to 0.33 of the vessel diameter were used: Rushton turbine (RT), Smith turbine (CD 6), or A 315 impeller. The measurements were carried out in coalescing and non-coalescing systems. Distilled water and aqueous solutions of an electrolyte (sodium chloride) of two different concentrations were used as the liquid phase. The gas phase was air. In the three-phase system, particles of sea sand were used as solid phase. The measurements were conducted at five different gas-flow rates and three particle loadings. Volumetric gas-liquid mass transfer coefficients were measured using the dynamic method. The presence and concentration of an electrolyte strongly affected the value of the gas-liquid mass transfer coefficient in both two- and three-phase systems. For all agitators used, significantly higher k l a coefficient values were obtained in the 0.4 kmol m−3 and 0.8 kmol m−3 aqueous NaCl solutions compared with the data for a coalescing system (with distilled water as the liquid phase). The k l a coefficient did not exhibit a linear relationship with the electrolyte concentration. An increase in the sodium chloride concentration from 0.4 kmol m−3 to 0.8 kmol m−3 caused a considerable decrease in the volumetric mass transfer coefficient in both the two-phase and three-phase systems. It was concluded that the mass transfer processes improved at a certain concentration of ions; however, above this concentration no further increase in k l a could be achieved.

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Effect of bubble contamination on gas–liquid mass transfer coefficient on CO2 absorption in amine solutions

Chemical Engineering Journal ◽

10.1016/j.cej.2007.04.036 ◽

2008 ◽

Vol 137 (2) ◽

pp. 422-427 ◽

Cited By ~ 25

Author(s):

Rocío Maceiras ◽

Sebastião S. Alves ◽

M. Ángeles Cancela ◽

Estrella Álvarez

Keyword(s):

Mass Transfer ◽

Transfer Coefficient ◽

Mass Transfer Coefficient ◽

Co2 Absorption ◽

Liquid Mass ◽

Liquid Mass Transfer ◽

Amine Solutions

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Numerical study of the hydrodynamics and mass transfer in the external loop airlift reactor

Chemical Industry and Chemical Engineering Quarterly ◽

10.2298/ciceq210522034k ◽

2021 ◽

pp. 34-34

Author(s):

Predrag Kojic ◽

Jovana Kojic ◽

Milada Pezo ◽

Jelena Krulj ◽

Lato Pezo ◽

...

Keyword(s):

Mass Transfer ◽

Transfer Coefficient ◽

Mass Transfer Coefficient ◽

Airlift Reactor ◽

Volumetric Mass Transfer Coefficient ◽

Cfd Model ◽

Gas Velocity ◽

Liquid Mass ◽

External Loop ◽

Liquid Mass Transfer

The objective of this study was to investigate the hydrodynamics and the gas-liquid mass transfer coefficient of an external-loop airlift reactor (ELAR). The ELAR was operated in three cases: different inlet velocities of fluids, different alcohols solutions (water, 0.5% methanol, 0.5% ethanol, 0.5% propanol and 0.5% butanol) and different concentration of methanol in solutions (0%, 0.5%, 1%, 2% and 5%). The influence of superficial gas velocity and various diluted alcohol solutions on hydrodynamics and gas-liquid mass transfer coefficient of the ELAR was studied. Experimentally, the gas hold-up, liquid velocities and volumetric mass transfer coefficient values in the riser and the downcomer were obtained from the literature source. A computational fluid dynamics (CFD) model was developed, based on two-phase flow, investigating different liquids regarding surface tension, assuming the ideal gas flow, applying the finite volume method and Eulerian-Eulerian model. The volumetric mass transfer coefficient was determined using CFD model, as well as artificial neural network model. The effects of liquid parameters and gas velocity on the characteristics of the gas-liquid mass transfer were simulated. These models were compared with appropriate experimental results. CFD model successfully succeed to simulate the influence of different alcohols regarding the number of C-atoms on hydrodynamics and mass transfer.

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