• Title, Summary, Keyword: Bubble Holdup

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Holdup Characteristics of Small Bubbles in a Viscous Slurry Bubble Column (점성슬러리 기포탑에서 작은 기포의 체류량 특성)

  • Jin, Hae-Ryong;Song, Yang-Ho;Kang, Yong;Jung, Heon;Lee, Ho-Tae
    • Korean Chemical Engineering Research
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    • v.49 no.1
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    • pp.83-88
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    • 2011
  • Holdup characteristics of small bubbles were investigated in a viscous slurry bubble column. The phase holdup of small bubbles was obtained from the knowledge of total bubble(gas) holdup and large bubble holdup, which were measured by mean of static pressure drop method and dual resistivity probe method, respectively. Effects of gas velocity, viscosity of continuous liquid phase and solid fraction in the slurry phase on the small bubble holdup as well as holdups of total bubble(gas) and large bubble in a viscous slurry bubble column. The small bubble holdup increased with increasing gas velocity but decreased with increasing liquid viscosity or solid fraction in the slurry phase. In addition the fraction of small bubble in the total bubble(gas) holdup increased with increasing gas velocity but decreased with increasing liquid viscosity or solid fraction in the slurry phase. It was revealed that the rising velocity of large bubble did not related to the holdup of small bubble in a viscous slurry bubble column.

Axial and Radial Distributions of Bubble Holdup in a Slurry Bubble Column with Pilot Plant Scale (파일럿규모 슬러리 기포탑에서 기포체류량의 축방향, 반경방향 분포)

  • Lim, Dae-Ho;Jang, Ji-Hwa;Kang, Yong;Jun, Ki-Won
    • Korean Chemical Engineering Research
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    • v.49 no.2
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    • pp.200-205
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    • 2011
  • Axial and radial distributions of bubble holdup were investigated in a slurry bubble column with pilot plant scale(D=1.0 m). Effects of gas velocity, surface tension of continuous liquid medium and solid fraction in the slurry phase on the axial and radial distributions of bubble holdup were examined. The bubble holdup decreased with increasing radial dimensionless distance from the center of the column, while it increased with increasing dimensionless distance in the axial direction from the distributor, in all the cases studied. The radial non-uniformity of bubble holdup increased with increasing gas velocity but decreasing surface tension of liquid medium, while it was not dependent upon the solid fraction in the slurry phase. The axial non-uniformity of bubble holdup increased with increasing gas velocity, but it does not change considerably with variations of liquid surface tension or solid fraction in the slurry phase . The axial and radial distributions of bubble holdup were well correlated in terms of operating variables within this experimental conditions.

Characteristics of Bubble Flow Behavior in a Gas-liquid Countercurrent Bubble Column Bioreactor (기-액 향류 흐름 기포탑 생물 반응기에서 기포 흐름 거동 특성)

  • Son, Sung-Mo;Kang, Suk-Hwan;Lee, Chan-Gi;Jung, Sung-Hyun;Kang, Yong;Kim, Sang-Done
    • Korean Chemical Engineering Research
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    • v.43 no.2
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    • pp.272-277
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    • 2005
  • Characteristics of bubbling behavior and bubble properties were investigated in a gas-liquid countercurrent bubble column of in diameter 0.152 m and 3.5 m in height, respectively. Effects of gas and liquid velocities and bubble distribution mode(even, wall-side, central or asymmetric distribution) on the bubble properties such as chord length, frequency, rising velocity and holdup in the reactor were measured and examined by means of dual resistivity probe method. The bubble size, frequency and holdup increased with increasing gas($U_G$) or liquid velocity($U_L$). The rising velocity of bubbles increased with increasing $U_G$, whereas decreased with increasing $U_L$. The uniformity of bubble size distribution and bubble holdup decreased when the distribution mode of bubbles at the gas distributor was changed from even to wall-side, central or asymmetric. The central distribution of bubbles was better than asymmetric mode but worse than wall-side distribution, in considering the bubble holdup and uniformity of distribution.

Axial and Radial Gas Holdup in Bubble Column Reactor

  • Wagh, Sameer M.;Ansari, Mohashin E. Alam;Kene, Pragati T.
    • Bulletin of the Korean Chemical Society
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    • v.35 no.6
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    • pp.1703-1705
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    • 2014
  • Bubble column reactors are considered the reactor of choice for numerous applications including oxidation, hydrogenation, waste water treatment, and Fischer-Tropsch (FT) synthesis. They are widely used in a variety of industrial applications for carrying out gas-liquid and gas-liquid-solid reactions. In this paper, the computational fluid dynamics (CFD) model is used for predicting the gas holdup and its distribution along radial and axial direction are presented. Gas holdup increases linearly with increase in gas velocity. Gas bubbles tends to concentrate more towards the center of the column and follows a wavy path.

Holdup Characteristics of Three Functional Regions in a Slurry Bubble Column (삼상 슬러리 기포탑의 세 기능영역 체류량 특성)

  • Jang, Ji Hwa;Lim, Dae Ho;Kang, Yong;Jun, Ki Won
    • Korean Chemical Engineering Research
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    • v.48 no.3
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    • pp.359-364
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    • 2010
  • Three kinds of functional regions such as continuous slurry(${\varepsilon}_f$), bubble(${\varepsilon}_b$) and wake(${\varepsilon}_w$) regions were identified, and the individual phase holdups of each functional region were determined in a three-phase slurry bubble column of 0.152 m ID. The holdups of bubble and wake were measured by adopting the electrical resistivity probe method. Effects of gas velocity and solid concentration in the slurry phase on the individual holdups of functional regions in the column were discussed. The holdup of continuous slurry phase decreased but that of bubble or wake increased, with an increase in the gas velocity in the column. The increase of solid content in the slurry phase could lead to the increase in the holdup of continuous slurry phase but decrease in the bubble or wake holdup. The portion of wake holdup was in the range of 15~40% of the bubble holdup, which decreased with increasing gas velocity or solid content in the slurry phase. The individual holdups of three functional regions were well correlated with operating variables within this experimental conditions.

Analysis of Hydrodynamic Similarity of Pressurized Three-Phase Slurry Bubble Column for its Design and Scale-up (가압 삼상슬러리 기포탑의 설계 및 Scale-up을 위한 수력학적 Similarity 해석)

  • Seo, Myung Jae;Lim, Dae Ho;Jin, Hae Ryong;Kang, Yong;Jung, Heon;Lee, Ho Tae
    • Korean Chemical Engineering Research
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    • v.47 no.6
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    • pp.720-726
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    • 2009
  • Hydrodynamic similarity was investigated in pressurized three-phase slurry bubble columns by selecting the bubble holdup and pressure drop as objective functions, for the effective design and scale-up of it. In addition, effects of operating variables on the bubble holdup with variation of column diameter were also analyzed. Gas velocity($U_G$), viscosity(${\mu}_{SL,eff}$) and surface tension(${\rho}_{SL}$) of slurry phase, density difference between the slurry and gas phases(${\rho}_{SL}-{\rho}_G$) depending on the operating pressure, pressure drop per unit length(${\Delta}P/L$), column diameter(D) and gravitational acceleration(g) were chosen as governing parameters in determining the bubble holdup and pressure drop in the column. From the dimensional analysis, four kinds of dimensionless groups were derived from the 7 parameters and 4 fundamental dimensions. Effects of dimensionless groups such as Reynolds, Froude and Weber numbers on the bubble holdup in the column were discussed. The pressure drop and bubble holdup could be predicted from the correlation of dimensionless groups effectively, which could be used as useful information for the design and scale-up of pressurized slurry bubble columns.

Gas holdup and hydrodynamic flow regime transition in bubble columns

  • Kim, Jun Young;Kim, Bongjun;Nho, Nam-Sun;Go, Kang-Seok;Kim, Woohyun;Bae, Jong Wook;Jeong, Sung Woo;Epstein, Norman;Lee, Dong Hyun
    • Journal of Industrial and Engineering Chemistry
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    • v.56
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    • pp.450-462
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    • 2017
  • The homogeneous-to-heterogeneous flow regime transition point dependence on gas and liquid properties was investigated in a semi-cylindrical bubble column of 1.8 m height and 0.21 m inner diameter operating as a semi-batch system. He, air, and $CO_2$ gases were injected at superficial gas velocities of up to 239 mm/s. The batch liquids included water, aqueous ethanol solutions, and aqueous glycerol solutions, all with a gas-free liquid height settled at 1 m. When the gas density increased, the gas holdup increased at all superficial gas velocities, delaying the flow regime transition. The gas holdups in the liquid mixtures were higher than those for tap water. The transition gas holdup for the ethanol solutions increased to a sharp maximum and then decreased as the surface tension increased. Also, the glycerol solutions showed similar behavior with respect to increasing liquid viscosity, but with a shallower maximum. The transition gas holdup was empirically correlated as a function of the gas density, surface tension, and liquid viscosity, employing dimensional constants. The measured transition gas holdups for liquid mixtures, as well as some data from the literature, were fitted by the correlation.

Effects of Column Diameter on the Holdups of Bubble, Wake and Continuous Liquid Phase in Bubble Columns with Viscous Liquid Medium (점성액체 기포탑에서 탑의 직경이 기포, wake 및 연속액상 체류량에 미치는 영향)

  • Lim, Dae Ho;Jang, Ji Hwa;Kang, Yong;Jun, Ki Won
    • Korean Chemical Engineering Research
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    • v.49 no.5
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    • pp.582-587
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    • 2011
  • Holdup characteristics of bubble, wake and continuous liquid phases were investigated in bubble columns with viscous liquid media. Effects of column diameter(0.051, 0.076, 0.102 and 0.152 m ID), gas velocity($U_G$=0.02~0.16 m/s) and liquid viscosity(${\mu}_L$=0.001~0.050 $Pa{\cdot}s$) of continuous liquid media on the holdups of bubble, wake and continuous liquid phases were discussed. The three phase such as bubble, wake and continuous liquid phases were classified successfully by adapting the dual electrical resistivity probe method. Compressed filtered air and water or aqueous solutions of CMC(Carboxy Methyl Cellulose) were used as a gas and a liquid phase, respectively. To detect the wake as well as bubble phases in the bubble column continuously, a data acquisition system(DT 2805 Lab Card) with personal computer was used. The analog signals obtained from the probe circuit were processed to produce the digital data, from which the wake phase was detected behind the multi-bubbles as well as single bubbles rising in the bubble columns. The holdup of bubble and wake phases decreased but that of continuous liquid media increased, with an increase in the column diameter or liquid viscosity. However, the holdup of bubble and wake phases increased but that of continuous media decreased with an increase in the gas velocity. The holdup ratio of wake to wake to bubble phase decreased with an increase in the column diameter or gas velocity, however, increased with an increase in the viscosity of con-tinuous liquid media. The holdups of bubble, wake and continuous liquid media could be correlated in terms of operating variables within this experimental conditions as: ${\varepsilon}_B=0.043D^{-0.18}U_G^{0.56}{\mu}_L^{-0.13}$, ${\varepsilon}_W=0.003D^{-0.85}U_G^{0.46}{\mu}_L^{-0.10}$, ${\varepsilon}_C=1.179D^{0.09}U_G^{-0.13}{\mu}_L^{0.04}$.

A Study on Gas Transfer of Viscous Aqueous Solutions in a Bubble Column (기포탑에서 점성수용액의 가스전달에 관한 연구)

  • 최일곤;김상렬
    • Journal of the Korean Society of Safety
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    • v.9 no.3
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    • pp.67-73
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    • 1994
  • The gas holdup and volumeteric liquid phase mass transfer coefficient with the variation of the concentration of CMC aqueous solution, gas velocity, diameter and area of the draught tube were investigated. As the results of the experiments, the gas holdup and volumetric liquid phase mass transfer coefficient decreased with decreasing the concentration of CMC aqueous solution, increased with increasing the gas velocity and increased with increasing the circulated area ratio of the draught tube.

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Size Verification of Small and Large Bubbles in a Bubble Column (기포탑에서 작은기포와 큰기포의 크기 구별)

  • Seo, Myung Jae;Jin, Hae-Ryong;Lim, Dae Ho;Lim, Ho;Kang, Yong;Jun, Ki-Won
    • Korean Chemical Engineering Research
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    • v.50 no.2
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    • pp.304-309
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    • 2012
  • Size verification of small and large bubbles in a bubble column was investigated by employing the dynamic gas disengagement (DGD) method and dual electrical resistivity probe (DRP) method, simultancously. The holdups of large and small bubbles in the bubble column in a given operating condition were obtained by means of the DGD method by measuring the pressure drop variation in the column with a variation of time after stopping the gas input into the column. The size and frequency of bubbles were measured by the DRP method in the same operating condition, from which the bubble holdup of each range of size was obtained. The verification of size in determining the large or small bubbles was decided by comparing the holdups of large or small bubbles measured by the DGD method with that measured by the DRP method. Filtered compressed air and tap water were used as a gas and a continuous liquid medium. The diameter and height of the bubble column were 0.102 m and 1.5 m, respectively. The demarcation size between the large and the small bubbles in the bubble column was 4.0~5.0 mm; the demarcation size was about 5.0 mm when the gas velocity was in the relatively low range, but about 4.0 mm when the gas velocity was in the relatively high range, within this experimental conditions.