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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.

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