A correlation for gas holdup in turbulent coalescing bubble columns

Abstract

A review of existing literature for the purpose of comparing correlations which allow Lhe explicit predictim @ gas holdup in twoor three-phase bubble columns shows wide disagreement concerning the eTfegt. of various variables. Further, various correlations, apparently of equal validity, show equally wide disagreement in the Fiadicted absolute values of gas holdup among three test systems; water-air, hydrocarbon solvent-air, and trichloroethyrene air. Some possible reasons for these disagreements are discussed.Extensive gas holdup data obtained in a 0.30 m diameter column for the three test systems were correlated statisticany for the transition and the turbulent region. The resulting correlation gives agreement with experiment to within *20%, with most data showing * 10% agreement. The proposed correlation was also tested against thirteen data sets (from eight researchers) which corresponded to its region of validity and gave good agreement. Three additional relevant data sets were not satisfactorily predicted.On a prockdk Ir une ktude bibliographique dans le but de comparer des corrklations permettant de prkdire explicitement la ktention des gaz dans des colonnes a bulles deux ou trois phases et on a montrk que ces codlations ne s'accordent pas sur I'effet des diffkrentes variables. De plus, diverses codlations, apparernment de mkme validitk, montrent kgalement un dksaccord dans les valeurs absolues prkdites pour la ktention des gaz dans le cas de trois systbmes-tests: eau -air, solvant a base d'hydrocarburesair et trichlokthylbneair. On analyse quelques raisons pouvant expliquer I . Air-Water Air-Glycol aq. soh. Air -Methanol 02-Water 2. Air-Alcohols Air-Halogenated Hydrocarbons 3. Air-Water Air-Glycerol, aq. soln. Air-Kerosene 4. (Air, H2, C02, CH4, C3Hw, N2) -Water Air -Organic Liquids Air-Electrolyte soln. U,, m/s 0.003 -0.4 UL, m/s 0 -0.044 D, rn 0.152 -0.6 H , m 1.26 -3.5 Single nozzle sparger d,,, rn 0.005 C = 0.2 for pure liquids and non-electrolyte mixtures Akita and Yoshida (1973) U,. m/s 0 -0.2 D, rn 0.1 H , rn > 1.2 Perforated plate d,,, rn 0.0005, 0.001 U,, rn/s 0.0014 -0.14 D, m 0.05, 0.07, 0.10 Perforated plate d,,, m 0.00087 -0.00309 Bach and Pilhofer (1978) Ex -= 0.115[ I -E, E , = 0.72! U -0.485 U z + 0.0975 U 3 u = U G [ p L / u ( p L -PO)^]''^ Kurnar et al. (1976) M = 21-49 u, pL 0 5 7 8 U,, m/s 0.012 -0.38 D, rn 0.1

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

“…Considering the complete U G range (Fig. 11, Table 2), our experimental measurements are in good agreement with the holdup data of the AG bubble column of (R2) and the data of Yoshida et al (Yoshida and Akita, 1965) (R11), Reilly et al (1986) (R13) and Schumpe and Grund (1986) (R14). The "AG" bubble column configuration studied by (R2) was obtained in this same facility but using inner pipes: the data are in very good agreement; further details may be found in Section 3.1.1.…”

“…The data of Akita and Yoshida (1973) (R4) are lower than our measurement, and the data of Otake et al (1981) (R5 and R6) agree with our measurement only up to U G ¼0.05 m/s. Finally, the data of Reilly et al (1986) (R12 and R13) and that of Kawase and Moo-Young (1987a) (R14) are comparable with our dataset: the former has higher holdup values, and the latter has lower.…”

“…Herein, we compare our results (in the batch mode) with a set of experimental studies with similar column diameters and sparger designs (Akita and Yoshida, 1973;Fair et al, 1962;Gopal and Sharma, 1983;Kawase and Moo-Young, 1987a;Otake et al, 1981;Reilly et al, 1986;Sada et al, 1984;Schumpe and Grund, 1986;Thorat et al, 1998;Ying et al, 1981;Yoshida and Akita, 1965). At first, we compare the data in the low U G range (Fig.…”

Reactor Modeling of a Slurry Bubble Column for Fischer-Tropsch Synthesis

“…The major effect of increased gas density is to stabilize the regime of homogeneous bubble flow and, consequently, to delay the transition to the churn-turbulent flow regime. It was observed (Reilly et al, 1986;Idogawa et al, 1987;Wilkinson and Van Dierendonck, 1990) that the gas holdup increases with gas density due to a reduction of bubble size. This was attributed to a decrease in bubble stability and a decrease in the coalescing rate with an increase in the gas density.…”

New Approaches for Theoretical Estimation of Mass Transfer Parameters in Both Gas-Liquid and Slurry Bubble Columns

“…The addition of an electrolyte to water is known to hinder coalescence with the result that smaller bubbles occur and a higher gas holdup than pure water. The addition of solids to a bubble column will in general lead to a small decrease in gas holdup (Reilly et al, 1986) and the formation of larger bubbles. The significant increase in gas holdup that occurs in two-phase bubble columns (due to the higher gas density) will also occur in three-phase bubble columns.…”