Gas Holdup, Axial Dispersion, and Mass Transfer Studies in Bubble Columns

Abstract

This article presents an extensive study on the gas holdup, axial liquid dispersion, and mass transfer for packed, trayed, and empty bubble columns. Four types of structured packings (Super-Pak, Flexipac, Mellapak, and Gauze) and two types of perforated partition trays (with 25% and 40% tray open area) were used to characterize the packed and trayed bubble columns, respectively. It was observed that the gas holdup and mass transfer characteristics of the packed and trayed bubble columns are superior to those of an empty bubble column, while the axial dispersion coefficients are much lower. This article discusses in detail the effect of the liquid and gas flow rates, liquid-phase viscosity, and type of internals. Additionally, experimental data of the packed, trayed, and empty bubble column are correlated by dimensionless numbers. Novel empirical correlations are proposed for the gas holdup, Bodenstein number (for the axial dispersion coefficient), and Stanton number (for the volumetric mass transfer coefficient), as a function of the Froude and Galileo dimensionless numbers.

Two-Phase Bubble Columns: A Comprehensive Review

“…Baawain et al [121], showed that the counter-current or co-current operating mode influenced ε G for about 5% of its weight, and less than 1% of its bubble size, showing that the effect observed is mainly caused by the bubble rise velocity and not only caused by the bubble size. In agreement with this explanation concerning the influence of U L on bubble motion, different studies have reported ε G decreasing in co-current operations [49,90,[122][123][124][125][126][127][128] and increasing in counter-current operations [48,49,128]. Biń et al [128] compared the three-operation mode showing that ε G increases with U L in counter-current mode and decreases or remains constant in co-current mode.…”

“…This method is based on the measurement of the liquid free surface before and after aeration. Another well-known method is based on the measurement of the differential pressure between two or more points in the column [80,86,114,116,122,123,125,126,135,141,170,179,194,198,209], under the hypothesis of negligible acceleration and friction pressure losses, as discussed by Leonard et al [1]. This method has been applied by a large number of authors.…”

Comprehensive experimental investigation of counter-current bubble column hydrodynamics: Holdup, flow regime transition, bubble size distributions and local flow properties

“…For example, Akita and Yoshida (1973) (d c ¼0.152 m, H c ¼2.5 m) observed a negligible effect of U L (up to 0.04 m/s) in both co-current and countercurrent operations. At higher liquid velocities, the column operation influences the holdup: the co-current mode reduces the holdup (Biń et al, 2001;Chaumat et al, 2005b;Jin et al, 2007;Kumar et al, 2012;Otake et al, 1981;Pjontek et al, 2014;Shah et al, 2012;Simonnet et al, 2007), and the counter-current mode increases the holdup (Besagni and Inzoli, 2016a;Besagni et al, 2014Biń et al, 2001;Jin et al, 2010;Otake et al, 1981) as bubbles are either accelerated or decelerated by liquid motion (Leonard et al, 2015;Rollbusch et al, 2015a). Baawain et al (2007) showed that the counter-current or cocurrent operation modes influenced the holdup by approximately 5% in weight, and less than 1% in bubble size, showing that the effect observed is mainly caused by the bubble rise velocity and not only the bubble size.…”

Unsaturated Polyesters and Vinyl Esters

“…In a series of recently published papers, the researchers describe a novel process for the synthesis of unsaturated polyester based on reactive distillation ( Figure 6.6 a, b, c) [17À21]. Reactive distillation combines the preparative step (synthesis) and the down-streaming step (separation) into one single operating unit and represents one of the most important applications of the multifactorial reactor concept [22].…”

“…The glycolyzated PET fragments can be then co-reacted with fresh unsaturated diacids (or anhydrides) and blended with styrene to produce superficial reinforcing of plastics, varnishes, binder for glass fiber mats and other applications [7]. Figure 6.6 (a) Process intensification: transferring the synthesis of unsaturated polyesters from tach processes to a reactive distillation process [17]; (b) Process intensification: Principal setup of reactive distillation process for the production of unsaturated polyesters [18]; and (c) Process intensification: Photograph of pilot plant scale reactive distillation equipment for unsaturated polyester production [18].…”