Mass transfer in multiphase agitated contactors

The objective of this work is to study the transfer of oxygen from gas to liquid phase in an electroflotation cell. The measurements were performed in a laboratory scale cell using insoluble electrodes, titanium coated with ruthenium oxide as anode and stainless steel as cathode. The volumetric mass transfer coefficient K L a, was characterized for clean tap water as liquid phase for different values of current density (J). The global coefficient of mass transfer based on the liquid film, K L , and the specific interfacial area, a, were characterized. A model which relates K L a to current density was established. Different evaluation criteria of oxygen transfer in electroflotation process were determined and compared with other aeration process.Keywords Current density Á Electroflotation Á Oxygen transfer Nomenclature a specific interfacial area (m 2 m -3 ) A gas-liquid interface area (m 2 ) C oxygen concentration in the liquid (g m -3 ) C * oxygen equilibrium concentration in the liquid (g m -3 ) C 0 initial dissolved oxygen concentration (g m -3 ) J current density (A m -2 ) d B bubble diameter (lm) F Faraday constant (C mol -1 ) H S static height of the liquid bed (m) H T total height of the gas -liquid bed (m) K L global coefficient of mass transfer based on liquid film (m s -1 ) K L a volumetric mass transfer coefficient (s -1 ) m O 2 oxygen flow rate (g s -1 ) M O 2 oxygen molar mass (g mol -1 ) OC oxygenation capacity (g m -3 h -1 ) RO oxygenation efficiency (%) S surface of the electrodes (m 2 ) T temperature of the liquid phase (°C) V aerated liquid volume (m 3 )Greek symbols e g gas hold-up (%) h empirical coefficient in Eq. (7)

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“…Nevertheless, the value will reach a limiting value. This is similar to previous studies of other types of gas-inducing contactor [26,27].…”

Section: The Global Coefficient Of Mass Transfer Based On Liquid Filmsupporting

confidence: 90%

Influence of current density on oxygen transfer in an electroflotation cell

Mansour¹,

Kolsi²,

Ksentini³

2007

J Appl Electrochem

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“…Most of them have adopted, with or without theoretical backgrounds, others definitions for making dimensionless k l a [11][12][13][14][15][16][17]. They include notably a modified Sherwood number (k l a · T 2 t /D) or Stanton number (k l a · V l /Q g ) [3].…”

Section: Introductionmentioning

confidence: 99%

A consistent dimensional analysis of gas–liquid mass transfer in an aerated stirred tank containing purely viscous fluids with shear-thinning properties

Hassan

Loubière

Legrand

et al. 2012

Chemical Engineering Journal

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Delaplace. A consistent dimensional analysis of gas-liquid mass transfer in an aerated stirred tank containing purely viscous fluids with shear-thinning properties. Chemical Engineering Journal, Elsevier, 2012Elsevier, , vol. 184, pp.42-56. <10.1016Elsevier, /j.cej.2011 a b s t r a c tThis paper deals with gas-liquid mass transfer in an aerated stirred tank containing Newtonian or shearthinning fluids. The aim is to demonstrate that, for a given mixing system, an unique dimensionless correlation gathering all the mass transfer rates (150 k l a measurements) can be obtained if and only if the variability of the rheological material parameters is correctly considered when implementing the theory of similarity. More particularly, it is clearly illustrated that a too gross simplification in the relevant list of the parameters characterizing the dependence of apparent viscosity with shear rates leads to pitfalls when building the -space set. This is then a striking example showing that a robust predictive correlation can be established when the non-constancy of fluid physical properties ceases to be neglected.

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“…This has been done to selectively grow the microorganism. After the inoculation, the bacteria was allowed to grow in incubator at 30 o C for Stirred Tank Albal et al [13].…”

Section: Biodegradation Studies Culture Preparationmentioning

confidence: 99%

“…Table 1 gives some of the correlations from literature for the volumetric coefficient for different reactor systems. It can be seen that different types of vessels / columns such as stirred tank [13], slurry bioreactor [16], airlift [22,23,26], bubble columns [14,15,17,18,20,21,27,28] have been used in mass transfer studies. In literature there have not been many reports on studies relating to the volumetric mass transfer coefficient for oxygen in biodegradation of phenol in bubble column bioreactors.…”

Section: Introductionmentioning

confidence: 99%