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Analysis of Holdup Characteristics of Large and Small Bubbles in Three-Phase Fluidized Beds by using a Dynamic Gas Disengagement Method

삼상유동층에서 동력학적 기체유출 측정방법에 의한 큰 기포와 작은 기포의 체류량 특성 해석

  • Lim, Hyun Oh (Graduate School of Green Energy Technology, Chungnam National University) ;
  • Lim, Dae Ho (Department of Chemical Engineering, Chungnam National University) ;
  • Seo, Myung Jae (Department of Chemical Engineering, Chungnam National University) ;
  • Kang, Yong (Graduate School of Green Energy Technology, Chungnam National University) ;
  • Jung, Heon (Korea Institute of Energy Research) ;
  • Lee, Ho Tae (Korea Institute of Energy Research)
  • 임현오 (충남대학교 녹색에너지 전문대학원) ;
  • 임대호 (충남대학교 화학공학과) ;
  • 서명재 (충남대학교 화학공학과) ;
  • 강용 (충남대학교 녹색에너지 전문대학원) ;
  • 정헌 (한국에너지기술연구원) ;
  • 이호태 (한국에너지기술연구원)
  • Published : 2011.10.01

Abstract

Phase holdup characteristics of relatively large and small bubbles were investigated in a three-phase(gasliquid-solid) fluidized bed of which diameter was 0.105 m(ID) and 2.5 m in height, respectively. Effects of gas(0.01~0.07 m/s) and liquid velocities(0.01~0.07 m/s) and particle size($0.5{\sim}3.0{\times}10^{-3}m$) on the holdups of relatively large and small bubbles were determined. The holdups of two kinds of bubbles in three phase fluidized beds were estimated by means of static pressure drop method with the knowledge of pressure drops corresponding to each kind of bubble, respectively, which were obtained by dynamic gas disengagement method. Dried and filtered air which was regulated by gas regulator, tap water and glass bead of which density was $2500kg/m^3$ were served as a gas, a liquid and a fluidized solid phase, respectively. The two kinds of bubbles in three-phase fluidized beds, relatively large and small bubbles, were effectively detected and distinguished by measuring the pressure drop variation after stopping the gas and liquid flow into the column as a step function: The increase slope of pressure drop with a variation of elapsed time was quite different from each other. It was found that the holdup of relatively large bubbles increased with increasing gas velocity but decreased with liquid velocity. However, the holdup showed a local minimum with a variation of size of fluidized solid particles. The holdup of relatively small bubbles increased with an increase in the gas velocity or solid particle size, while it decreased slightly with an increase in the liquid velocity. The holdups of two kinds of bubbles were well correlated in terms of operating variables within this experimental conditions, respectively.

내경이 0.105 m이고 높이가 2.5 m인 삼상(기체-액체-고체) 유동층에서 상대적으로 큰 기포와 작은 기포의 체류량 특성을 고찰하였다. 기체유속(0.01~0.07 m/s), 액체유속(0.01~0.07 m/s) 그리고 입자크기($0.5{\sim}3.0{\times}10^{-3}m$)가 상대적으로 큰 기포와 작은 기포의 체류량에 미치는 영향을 검토하였다. 삼상 유동층에서 이들 두 종류 기포들의 체류량은 동력학적 기체 유출 방법(Dynamic gas disengagement method)에 의해 측정된 각각 기포들에 의한 압력강하 정보로부터 정압강하법(static pressure drop method)에 의해 산출되었다. 기체조절기에 의해 조절되는 건조되고 여과된 공기와 물 그리고 밀도가 2,500 $kg/m^3$인 유리구슬을 각각 기체, 액체 및 고체유동입자로 사용하였다. 삼상유동층에서 이들 두 종류의 기포, 즉 상대적으로 큰 기포와 작은 기포들은 유동층 탑에 유입되는 기체와 액체의 흐름을 정지시킨 후 경과시간에 따른 탑 내부의 압력강하를 측정함으로써 효과적으로 조사하고 분리할 수 있었다. 이들 두 종류의 기포들은 경과시간에 따라 증가하는 압력강하의 기울기가 서로 매우 다르게 나타났다. 실험결과 상대적으로 큰 기포들의 체류량은 기체의 유속이 증가함에 따라 증가하였으나 액체의 유속이 증가함에 따라서는 감소하였다. 그러나, 이들 큰 기포의 체류량은 유동입자의 크기가 변화함에 따라 국부적인 최소값을 나타내었다. 상대적으로 작은 기포들의 체류량은 기체유속 또는 고체입자의 크기가 증가함에 따라 증가하였으나 액체의 유속이 증가함에 따라서는 약간 감소하였다. 이들 두 종류 기포들의 체류량들은 각각 본 연구의 실험 범위 내에서 조작변수들의 상관식으로 나타낼 수 있었다.

Keywords

References

  1. Fan, L. S., Gas-Liquid-Solid Fluidization Engineering, Butterworths, Stonehair, Ma.(1989).
  2. Kim, S. D. and Kang, Y., "Heat and Mass Transfer in Threephase Fluidized Beds; An Overview," Chem. Eng. Sci., 52(21-22), 3639-3660(1997). https://doi.org/10.1016/S0009-2509(97)00269-8
  3. Kim, S. D. and Kang, Y., "Hydrodynamic, Heat and Mass Transfer in Inverse and Circulating Three-phase Fluidized-bed Reactors for Waste Water Treatment," Stud. Surf. Sci. Catal., 159, 103-108(2006). https://doi.org/10.1016/S0167-2991(06)81545-4
  4. Kang, Y., Lee, K. I., Shin, I. S., Son, S. M., Kim, S. D. and Jung, H., "Characteristics of Hydrodynamics, Heat and Mass Transfer in Three-phase Inverse Fluidized Beds," Korea Chem. Eng. Res. (HWAHHAK KONGHAK), 45, 451(2008).
  5. Lefebvre, S., Guy, C. and Chaouki, J., "Solid Phase Hydrodynamics of Three-phase Fluidized Beds-a Convective/dispersive Mixing Model," Chem. Eng. J., 133(1-3), 85-95(2007). https://doi.org/10.1016/j.cej.2007.02.004
  6. Kim, S. D. and Kang, Y., "Dispersion Phase Characteristics in t Hree-phase Fluidized Beds", Mixed Flow Hydridynamics, Advanced Eng. Fluid Meckanics Series, Gulf Pub. Co. New York(1996).
  7. Wild, G., Saberian, M., Schwarty, J. and Charpentier, J. E., "Gas-liquid-solid Fluidized-bed Reactors: State of Art and Industrial Possibilities," Int'L Chem. Eng., 24, 639(1984).
  8. Lee, K. I., Son, S. M., Kim, U. Y., Kang, S. H., Kang, Y. and Kim, S. D., "Particle Dispersion in Viscous Three-phase Inverse Fluidized Beds," Chem. Eng. Sci., 62, 7060(2007). https://doi.org/10.1016/j.ces.2007.08.024
  9. Shin, K. S., Song, P. S., Lee, C. G., Kang, S. H., Kang, Y., Kim, S. D. and Kim, S. J., "Heat Transfer Coefficient in Viscous Liquid- solid Circulation Fluidized Beds," AIChE J., 51(2), 671-677 (2005). https://doi.org/10.1002/aic.10291
  10. Lin, T. J. and Chiu, H. T., "Effects of Macroscopic Hydrodynamics on Heat Transfer in a Three-phase Fluidized Bed," Cataly. Today, 79-80, 159-167(2003). https://doi.org/10.1016/S0920-5861(03)00021-X
  11. Cho, Y. J., Song, P. S., Kim, S. H., Kang, Y. and Kim, S. D., "Stochastic Analysis of Gas-liquid-solid Flow in Three-phase Circulating Fluidized Beds," J. Chem. Eng. Japan., 34(2), 254-261(2001). https://doi.org/10.1252/jcej.34.254
  12. Son, S. M., Kang, S. H., Kang, Y. and Kim, S. D., "Characteristics of Particle Flow and Heat Transfer in Liquid-particle Swirling Fluidized Beds," Korean Chem. Eng. Res.(HWAHHAK KONGHAK), 44(5), 505-512(2006).
  13. Son, S. M., Shin, H. J., Kang, S. H., Kang, Y. and Kim, S. D., "Characteristic of Phase Holdups and Pressure Fluctuations in a Three-phase Swirling Fluidized Bed," J. Korean Ind. Eng. Chem. 15(6), 652-658(2004).
  14. Wan, L., Alvaregcuenca, M., Upreti, S. R. and Lohi, A., "Development of a Three-phase Fluidized Bed Reactor with Enhanced Oxygen Transfer," Chem. Eng. Processing : Process Intensification, Doi: 10. 1016/J. Cep. 2009. 10. 012(2009).
  15. Ramesh, K. V., Raju, G. M. J., Sarma, G. V. S. and Sarma, C. B., "Effect of Internal on Phase Holdups of a Three-phase Fluidized Bed," Chem. Eng. J., 145, 393(2009). https://doi.org/10.1016/j.cej.2008.08.023
  16. Jena, H. M., Roy, G. K. and Meikap, B. C., "Prediction of Gas Holdup in a Three-phase Fluidized Bed from Bed Pressure Drop Measurement," Chem. Eng. Res. Des., 86, 1301(2008). https://doi.org/10.1016/j.cherd.2008.05.007
  17. Deckwer, W. D., Bubble Column Reactors, John Wiley And Sons. Ny(1992).
  18. Krichna, R. and Sie, S. T., "Design and Scale-up of the Fischertropsch Bubble Column Slurry Reactor," Fuel Processing Technol., 64, 73(200). https://doi.org/10.1016/S0378-3820(99)00128-9