Experimental investigation of the influence of column scale, gas density and liquid properties on gas holdup in bubble columns

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

“…Hills (1976) mentioned that if U L is low compared with the bubble rise velocities, no impact of the liquid velocity on holdup is expected because the acceleration of the bubbles will be negligible. This hypothesis is confirmed by using the approach of Rollbusch et al (2015a): the bubble swarm velocities (Section 3.2) are comparable with the liquid velocities.…”

“…Low liquid velocities do not affect the holdup-as found by several investigators (Akita and Yoshida, 1973;de Bruijn et al, 1988;Lau et al, 2004;Rollbusch et al, 2015a;Sangnimnuan et al, 1984;Shah et al, 1982;Shawaqfeh, 2003;Voigt and Schügerl, 1979;Yang and Fan, 2003)-because, if U L is low compared with the bubble rise velocities, the acceleration of the bubbles is negligible (Hills, 1976). 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.…”

“…11, Table 2). When comparing holdup data between different configurations-at the same operating conditions (i.e., atmospheric pressure and temperature)-some design parameters must be considered (Rollbusch et al, 2015a):…”

“…Another parameter that should be considered is the water quality, as stated by Kemoun et al (2001) and remarked by Rollbusch et al (2015a): if tap water is used, its qualities differ from location to location; if deionized water is used, the qualities may differ from day to day, and remnants of used liquids and dirt may be present and affect the results. The interested reader may refer to the discussion of Rollbusch et al (2015a).…”

“…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.…”