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삼상 순환유동층에서 기체-액체 물질전달 특성

Mass Transfer Characteristics of Three-Phase Circulating Fluidized Beds

김사중 조용준 강용^† 김상돈¹ 박성희²

Sa-Jung Kim Yong-Jun Cho Yong Kang^† Sang-Done Kim¹ Sung-Hee Park²

충남대학교 화학공학과, 대전 305-764 ¹한국과학기술원 화학공학과, 대전 305-701 ²우석대학교 화학공학과, 청주 565-701

Department of Chemical Engineering, Chungnam, National University, Daejeon 305-764, Korea ¹Department of Chemical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea ²Department of Chemical Engineering, Woosuk University, Cheonju 565-701, Korea

HWAHAK KONGHAK, October 2001, 39(5), 613-618(6), NONE

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Abstract

삼상 순환유동층의 상승관(내경이 0.102 m이고 높이가 3.5 m)에서 기체-액체 부피물질전달 계수(k(L)a)의 특성을 고찰하였다. 기체 (0.01-0.09 m/s)및 액체유속(0.12-0.43 m/s), 고체순환속도(2-8 kg/m(2)s) 그리고 고체 유동입자의 크기(1.0-1.3 mm)가 기체-액체 부피 물질전달 계수에 미치는 영향을 검토하였다. 기체-액체 물질전달 계수는 용존산소의 축방향 농도 분포로부터 축방향 분산 모델에 의해 구하였다. 물과 여과된 압축공기 그리고 밀도가 2,500 kg/m(3)인 유리구슬을 액체상, 기체상 그리고 유동 고체입자로 각각 사용하였다. 상승관에서 기체의 유속이 기체-액체 부피 물질전달 계수의 결정에 가장 중요한 요소로 나타났다. 즉, 부피 물질전달 계수는 기체유속이 증가함에 따라 증가하였으나, 액체 유속의 변화에 따라서는 유동입자의 크기가 비교적 큰 1.7-3.0 mm의 유동층에서 크게 변화하지 않았다. 다만, 유동입자의 크기가 1 mm인 경우에는 액체유속이 증가함에 따라 k(L)a 값이 약간 증가하는 것으로 나타났다. 기체-액체 부피 물질전달 계수는 고체순환속도와 유동입자의 크기가 증가함에 따라 증가하는 것으로 나타났다. 기체-액체 물질전달 계수는 본 연구의 실험범위에서 운전변수와 무차원군의 함수로 각각 나타낼 수 있었다.

Characteristics of gas-liquid volumetric mass transfer has been investigated in a riser of three-phase circulating fluidized bed(0.102 m ID and 3.5 m in height). Effects of gas(0.01-0.09 m/s) and liquid(0.12-0.43 m/s) velocities, solid circulation rate(2-8 kg/m(2)s) and fluidized particle size(1.0-3.0 mm) on the volumetric gas-liquid mass transfer coefficient have been examined. The mass transfer coefficient has been recovered from the concentration profile of dissolved oxygen in the axial direction of the riser by means of axial dispersion model. Tap water, filtered and compressed air and glass bead whose density is 2,500 kg/m(3) were employed as a liquid, gas and solid phase, respectively. It has been found that the gas velocity is a important factor to determine the value of mass transfer coefficient; the mass transfer coefficient increases with increasing gas velocity but it dose not change considerably with the variation of liquid velocity in the beds of relatively large particle(d(P): 1.7-3.0 mm), although the k(L)a value increases slightly with increasing U(L) in the beds of 1 mm glass bead. The value of mass transfer coefficient increases with increasing solid circulation rate as well as particle size. The mass transfer coefficient has been correlated as a function of operation variables as well as dimensionless groups.

Keywords

Three-Phase Circulating Fluidized Bed Gas-Liquid Mass Transfer Mass Transfer Coefficient Axial Dispersion-Model Correlation

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