Effect of Spreading Coefficient on Gas-Liquid Mass Transfer in Gas-Liquid-Liquid Dispersions in a Stirred Tank

Pinho, Henrique J. O.; Alves, Sebastião S.

doi:10.1080/00986445.2010.485011

Cited by 9 publications

(6 citation statements)

References 13 publications

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“…All these figures show that K hep G does not depend upon composition at low values of x hep , but that it increases abruptly and dramatically at a value of x hep that has been shown previously (Pinho and Alves, 2010) to be close to the composition at which the system changes from the non-spreading to the spreading regime (x hep % 0.75 AE 0.05). Above this value of x hep , gas-liquid mass transfer of heptane becomes so efficient that the gas leaves the stirred mixture close to saturation, preventing calculation of (K G a) hep with accuracy ((K G a) hep ''close'' to infinity).…”

Section: Heptane Mass Transfersupporting

confidence: 64%

Gas Absorption in Stirred Gas-Liquid-Liquid Systems: Effect of Transferred Solute Solubility and Oil Phase Spreading Characteristics

Alves

Pinho

2013

Chemical Engineering Communications

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The effect on gas-liquid mass transfer of dispersing an oil phase in water in an aerated stirred tank is not predictable, because the mechanisms involved are not well understood. To try to elucidate these mechanisms, a set of experiments was carried out that included: (i) measurement of the effect of oil addition on gas dispersion properties, (ii) quantification of mass transfer of two solutes (heptane and oxygen) with very different solubilities in the liquid phases, and (iii) variation of the spreading characteristics of the oil phase, which consisted of mixtures of dodecane and heptane in varying concentrations. It was found that in the case of heptane mass transfer, when the oil spreading coefficient S changes from negative to positive, the outlet gas becomes practically saturated, corresponding to a several-fold increase in mass transfer coefficient. In the case of oxygen mass transfer, the effect of S is not as dramatic, but it is also quite significant. For a spreading oil phase (S > 0), the mass transfer coefficient decreases upon trace oil addition, going through a minimum as oil holdup increases, and then increasing steadily. In the case of a non-spreading oil phase, mass transfer coefficient initially increases with oil holdup increase, going through a maximum and then decreasing. Comparison between mass transfer coefficients for the two solutes indicates that k L a for heptane is larger than that of oxygen by a margin not explainable through the difference in diffusivities, which is evidence for a difference in transfer paths=mechanisms. A physical interpretation compatible with these results is offered.

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Section: Heptane Mass Transfersupporting

confidence: 64%

Gas Absorption in Stirred Gas-Liquid-Liquid Systems: Effect of Transferred Solute Solubility and Oil Phase Spreading Characteristics

Alves

Pinho

2013

Chemical Engineering Communications

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“…The increase in k L a at 15% n-heptane volume fraction (+336% as compared to water) can probably be explained by the bubble-covering mechanism proposed by Rols et al [19]. This mechanism is linked to the spreading coefficient S. Pinho and Alves [11] recently concluded that there is direct contact between gas and oil when S > 0, and very high mass transfer coefficients can be expected. The high S value for n-heptane (Table 2) might enable n-heptane to spread as a film on the oxygen bubbles.…”

Section: Effect Of Oil Volume Fraction On K L Amentioning

confidence: 90%

Oxygen Absorption into Stirred Emulsions of n-Alkanes

Ngo

Schumpe

2012

International Journal of Chemical Engineering

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Absorption of pure oxygen into aqueous emulsions of n-heptane, n-dodecane, and n-hexadecane, respectively, has been studied at 0 to 100% oil volume fraction in a stirred tank at the stirring speed of 1000 min−1. The volumetric mass transfer coefficient, , was evaluated from the pressure decrease under isochoric and isothermal (298.2 K) conditions. The O/W emulsions of both n-dodecane and n-hexadecane show a maximum at 1-2% oil fraction as reported in several previous studies. Much stronger effects never reported before were observed at high oil fractions. Particularly, all n-heptane emulsions showed higher mass-transfer coefficients than both of the pure phases. The increase is by upto a factor of 38 as compared to pure water at 50% n-heptane. The effect is tentatively interpreted by oil spreading on the bubble surface enabled by a high spreading coefficient. In W/O emulsions of n-heptane and n-dodecane increases with the dispersed water volume fraction; the reason for this surprising trend is not clear.

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“…Although these parameters are studied quite intensively for L‐L systems, there is very limited information about the influence of such parameters when G‐L‐L systems in stirred tanks are set up 23, 65; therefore, scale‐up of multiphase bioprocesses is extremely difficult 56. For instance, Alves and Pinho 32 and Pinho and Alves 66 investigated the G‐L mass transfer of dispersing an oil phase in water during aeration in a stirred tank. They found that the heptane mass transfer coefficient increases several‐fold when the oil spreading coefficient changes from negative to positive.…”

Section: Introductionmentioning

confidence: 99%

Aeration of Liquid‐Liquid Systems Using Various Agitators in a Mixer Equipped with a Membrane Diffuser

Szaferski

Mitkowski

2016

Chem Eng & Technol

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Efficient aeration of liquid mixtures is essential in many biochemical and chemical processes. The power requirements needed to obtain three-phase gas-liquid-liquid systems containing air, mineral oil, and water as modeling mixture were analyzed. The influence of using various kinds of agitators consisting of two stirrers on a common shaft and different volume fractions of oil ranging from 0.111 to 0.429 were investigated experimentally. The studies were performed for three configurations of stirrers consisting of Smith disc, Rushton, or flat-blade turbines.

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Effect of Spreading Coefficient on Gas-Liquid Mass Transfer in Gas-Liquid-Liquid Dispersions in a Stirred Tank

Cited by 9 publications

References 13 publications

Gas Absorption in Stirred Gas-Liquid-Liquid Systems: Effect of Transferred Solute Solubility and Oil Phase Spreading Characteristics

Gas Absorption in Stirred Gas-Liquid-Liquid Systems: Effect of Transferred Solute Solubility and Oil Phase Spreading Characteristics

Oxygen Absorption into Stirred Emulsions of n-Alkanes

Aeration of Liquid‐Liquid Systems Using Various Agitators in a Mixer Equipped with a Membrane Diffuser

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