HWAHAK KONGHAK, Vol.34, No.4, 511-518, August, 1996
기-액병류상향 충전탑에서 기-액흐름양상과 액체의 흐름 및 축방향혼합특성
Gas-Liquid Flow Pattern, Liquid Flow, and Axial Mixing Characteristics in a Packed Column with Gas-Liquid Cocurrent Upflow
초록
기-액흐름이 병류상향으로 흐르는 충전탑에서 기-액흐름양상과 액체의 흐름 및 축방향혼합특성을 연구하였다. 실험은 공기-물계에서 기-액흐름양상의 전이조건과 액체의 체류시간분포(RTD)를 측정하였다. 측정된 RTD로부터 제시된 3가지혼합모델, 즉 축방향분산모델(ADM), 정체지역이 존재하는 플러그흐름모델(PFM)과 정체지역이 존재하는 축방향분산모델(DSM)을 사용하여 혼합모델의 매개변수들을 산출하였다. 그리고 조업조건에 따른 각 혼합모델의 적용성과 매개변수들을 해석하였다. 실험결과, 기포흐름에서 맥동흐름으로 전이되는 기체속도는 액체속도가 증가할수록, 그리고 충전물인 유리구슬의 직경이 작을수록 증가하였으며 액체의 흐름과 혼합특성은 모델DSM으로 잘 해석할 수 있었다. 또한 곡선맞춤법으로 산출된 정체지역의 분율은 액체속도가 증가할수록 감소하였으나 유동지역과 정체지역간의 물질전달계수는 기체 및 액체속도의 증가에 따라 증가하였다. 그리고 모델 ADM과 모델DSM으로 산출된 유동지역에서의 Peclet수는 액체속도가 증가할수록, 그리고 충전물의 직경이 작을수록 증가하였다. 이때 조업조건에 따른 이들 매개변수에 대한 상관식을 얻었다.
For upward cocurrent gas-liquid flow in a packed column, the gas-liquid flow pat- tern, liquid flow, and axial mixing characteristics were investigated. The transition boundary of gas-liquid flow pattern and residence time distribution(RTD) of liquid phase were measured in an air-water system. Based on experimental RTDs, parameters of mixing models were evaluated with three proposed mixing models : axial dispersion model(ADM), plug flow model with stagnant zone(PFM), and axial dispersion model with stagnant zone(DSM). Accordingly, the applicability and parameters of each mixing model were analyzed for various operating conditions. We found that the gas velocity at bubble-pulse flow transition boundary was increased with increasing liquid velocity and decreasing diameter of glass bead as a packing material, and that the flow and mixing characteristics of liquid phase could be well analyzed by DSM. Also, the fraction of stagnant zone estimated by the curve fitting method was decreased with increasing liquid velocity, while the mass transfer coefficient between dynamic and stagnant zones was increased with increasing gas and liquid velocities. In dynamic zone, the calculated Peclet numbers in both ADM and DSM were increased with increasing liquid velocity and decreasing diameter of glass bead. In these conditions, correlations of these parameters were obtained for various operating conditions.
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