Gas—liauid mass transfer in three‐phase stirred tank reagors: Newtonian and non‐newtonian fluids

Abstract

Gas-liquid mass transfer has been investigated in gas-liquikolid three-phase stirred tank reactors with Newtonian and non-Newtonian liquids. Volumetric mass transfer coefficients and gas hold-ups were measured in a 0.2 m i.d. stirred tank reactor and the effects of low-density polymeric particles (p, =lo30 and 1200 kg/m3; up to 15 ~0 1 % ) on gas-liquid mass transfer were examined. The volumetric mass transfer coefficients in water were found to decrease due to the presence of solid particles at constant impeller speed and superficial gas velocity. On the other hand, solids loading led to higher mass transfer rates in non-Newtonian carboxymethyl cellulose aqueous solutions. Our previously proposed model for mass transfer in gas-liquid two-phase systems was extended to gasliquid-solid three-phase systems. Reasonable agreement was found between the predictions of the proposed model and the experimental data. ~On a etudie le transfert de matiere gaz-liquide dans des reacteurs a reservoirs agites gaz-liquide-solide triphasiques avec des liquides newtoniens et non newtoniens. Les coefficients volumetriques de transfert de matiere et les retentions de gaz ont ete mesurees dans un reacteur a reservoir agite de 0,2 de diametre interieur, et on a examine les effets de particules polymtkiques de faible densite (p, = 1030 et 1200 kg/m3; jusqu'a 15% en volume) sur le transfert de matiere gazliquide. On a trouve que les coefficients volumetriques de transfert de matiere dans I'eau diminuaient du fait de la presence de particules solides a vitesse de turbine et vitesse de gaz superficielle constantes. Par ailleurs, on a note que le chargement en solides menait a de plus grandes vitesses de transfert de matiere dans des solutions aqueuses non newtoniennes de carboxymethyl cellulose. Notre ancien modele propose pour le transfert de matiere dans des systemes gazliquide biphasiques a ete etendu h des systemes gaz-liquide-solides triphasiques. Un accord raisonnable a ete trouve entre les predictions du modele propose et les donnees experimentales.

Mass Transfer in a Flat Gas/Liquid Interface using non‐Newtonian Media

“…These deviations are not high if it is consider that the absorbent phases had a non-Newtonian behavior with several difficulties in analyzing the characteristics of these fluids in the contactor. The deviations found by other authors for similar systems employing non-Newtonian media have been around ± 30 % [20]. Using these values, the proposed equations to estimate the mass transfer coefficients for these systems reproduce, in an acceptable manner, the experimental values and produce satisfactory results.…”

Gas Dispersion and Solid Suspension in a Three-Phase Stirred Tank With Multiple Impellers

“…Most previous research has focused on the solid suspension or power consumption in a multi-impeller three-phase system with impellers of the traditional Rushton or pitched-blade turbine types (Dutta and Pangarkar, 1995;Saravanan et al, 1997;Armenante et al, 1999;Dohi et al, 2001). The results reflect confusion about the effect of solids on gas holdup and gas-liquid mass transfer, with conflicting results indicating an increase, decrease, or no effect on the gas holdup and mass transfer coefficients in three-phase systems (Kawase et al, 1997a). The present work with a three-impeller agitator stirred tank focuses on the performance of various impeller combinations and the effects of solids concentration and gas inlet flow rate on the just-suspending agitation speed, gas holdup, and power consumption.…”

Palladium supported on bacterial biomass as a novel heterogeneous catalyst: A comparison of Pd/Al2O3 and bio-Pd in the hydrogenation of 2-pentyne

“…Detailed analysis of the mass transfer resistances occurring during hydrogenation of pentyne has been presented by Bennett et al (2009), including calculations of mass transfer coefficients for the gas bubble-liquid (k L a) and liquid-solid (k c ) for the reaction in isopropanol using the correlations of Kawase et al (1997) and Grisafi et al (1998), respectively. A summary of the mass transfer calculations reported by Bennett et al (2009) is provided in Table 2 for the purposes of comparison with the experimental data reported here.…”