공기부양반응기(airlift reactor) 내의 액체순환속도(liquid circulation velocity)를 예측하기 위한 수학적 모형이 유체순 환고리(fluid circulation loop)에 대한 기계적 에너지 수지를 기초로 개발되었다. 그 모형은 90° 방향전환으로 인한 에 너지 손실과 반응기의 각 부위에서의 마찰로 인한 에너지 손실 그리고 단면적의 변화로 인한 에너지 손실을 모두 고 려하였다. 마찰과 방향전환 그리고 단면적 변화에 의한 손실계수를 각각 고려한 모형이 집중매개변수(lumped parameter)를 사용한 기존의 모형보다 액체순환속도를 더 잘 예측할 수 있었다. 순환액체속도는 추적자펄스방법(tracer pulse method) 으로 측정하였다. 개발된 모형은 상하부에 연결관(connecting pipe)을 갖는 외부순환 공기부양반응기에서 얻은 본 연구의 실 험 결과의 대부분은 물론이고 다양한 형태의 공기부양반응기에서 얻어진 다른 연구자들의 결과도 ±20%이내의 오차로 잘 예측할 수 있었다. 외부 및 내부순환 공기부양반응기에서 순환유체의 90° 방향전환과 관련된 손실계수에 대한 유용한 실험식을 구하여 액체순환속도를 예측하는 데 사용하였다.

A mathematical model for predicting the liquid circulation velocity in an airlift reactor was developed based on the mechanical energy balance of the fluid circulation loop. The model considered the energy loss due to a 90° turn, the energy loss due to friction, and the energy loss due to the change in cross-sectional area at each part of the reactor. The model that separately considered the loss coefficients related to friction, direction change, and crosssectional area change was able to predict the liquid circulation velocity better than the previous model using lumped parameters. The liquid circulation velocity was measured by the tracer pulse method. Most of our experimental results obtained in external-loop airlift reactors, which had the top and bottom connecting pipes, as well as other investigators' results obtained in various types of airlift reactors, were well predicted by the developed model with an error within 20%. Useful empirical equations for the loss coefficient related to the 90° turn of the circulating fluid were obtained in external and internal-loop airlift reactors and used to predict the liquid circulation velocity.

Airlift reactor Liquid circulation velocity Energy balance Hydrodynamics Loss coefficients

1. Jones, A. G., “Liquid Circulation in a Draft-Tube Bubble Column,” Chem. Eng. Sci., 40, 449-462(1985).
2. Verlaan, P., Tramper, J. and Riet, K. V., “A Hydrodynamic Model for an Airlift-Loop Bioreactor with External Loop,” Chem. Eng.
J., 33, B43-B53(1986).
3. Chisti, M. Y., Halard, B. and Moo-Young, M., “Liquid Circulation in Airlift Reactors,” Chem. Eng. Sci., 43, 451-457(1988).
4. Chisti, M. Y. and Moo-Young, M., “Prediction of Liquid Circulation Velocity in Airlift Reactors with Biological Media,” J.Chem. Tech. Biotechnol., 42, 211-219(1988).
5. García-Calvo, E., “A Fluid Dynamic Model for Airlift Loop Reactors,” Chem. Eng. Sci., 44(2), 321-323(1989).
6. Kemblowski, Z., Przywarski, J. and Diab, A., “An Average Gas Holdup and Liquid Circulation in Airlift Reactors with External Loop,” Chem. Eng. Sci., 48(23), 4023-4035(1993).
7. Metzner, A. B. and Reed., J. C., “Flow of Non-Newtonian Fluids-Correlation of the Laminar, Transition and Turbulent-Flow Regions,” AIChE J., 1(4), 434-440(1955).
8. García-Calvo, E. and Letón, P., “Prediction of Gas Hold-Up and Liquid Velocity in Airlift Reactors Using Two-Phase Flow Friction Coefficients,” J. Chem. Tech. Biotechnol., 67, 388-396(1996).
9. Wallis, G. B., One Dimensional Two Phase Flow, McGraw-Hill,New York(1969).
10. McCabe, W. L, Smith, J. C. and Harriott, P., Unit Operations of Chemical Engineering, 6th ed., McGraw-Hill, New York(2001).
11. Choi K. H., “Effect of Unaerated Liquid Height on Hydrodynamic Characteristics of an External-Loop Airlift Reactor,”Chem. Eng. Comm., 189, 25-42(2002).
12. Rujiruttanakul, Y. and Pavasant, P., “Influence of Configuration on the Performance of External Loop Airlift Contactors,”Chem. Eng. Res. Des., 89, 2254-2261(2011).
13. Al-Masry, W. A. and Dukkan, A. R., “The Role of Gas Disengagement and Surface Active Agents on Hydrodynamic and Mass Transfer Characteristics of Airlift Reactors,” Chem. Eng. J., 65,263-271(1997).
14. Bentifraouine, C., Xuereb, C. and Riba, J. P., “An Experimental Study of the Hydrodynamic Characteristics of External Loop Airlift Contactors,” J. Chem. Tech. Biotechnol., 69, 345-349(1997a).
15. Bentifraouine, C., Xuereb, C. and Riba, J. P., “Effect of Gas Liquid Separator and Liquid Height on the Global Hydrodynamic Parameters of an External Loop Airlift Contactor,” Chem. Eng.J., 66, 91-95(1997b).
16. Merchuk, J. C. and Stein, Y., “Local Hold-Up and Liquid Velocity in Air-Lift Reactors,” AIChE J., 27, 377-388(1981).
17. Krichnavaruk, S. and Pavasant, P., “Analysis of Gas-Liquid Mass Transfer in an Airlift Contactor with Perforated Plates,” Chem.Eng. J., 89(1-3), 203-211(2002).
18. Couvert, A., Bastoul, D., Roustan, M., Line, A. and Chatellier,P., “Prediction of Liquid Velocity and Gas Hold-Up in Rectangular Air-Lift Reactors of Different Scales,” Chem. Eng. Prec.,40, 113-119(2001).
19. Lu, W. J. and Hwang, S. J., “Liquid Velocity and Gas Holdup in Internal Loop Airlift Reactors with Low-Density Particles,”Chem. Eng. Sci., 50, 1301-1310(1995).
20. Petrović, D. Lj., Pošarac, D., Duduković, A. and Skala, D.,“Hydrodynamics and Mass Transfer in a Draft Tube Bubble Column,” J. Serb. Chem. Soc., 56, 227-240(1991).
21. Siegel, M. and Merchuk, J. C., “Hydrodynamics in Rectangular Air-Lift Reactors: Scale-Up and Influence of Gas-Liquid Separator Design,” Can. J. Chem. Eng., 69(2), 465-473(1991).
22. Wachi, S., Jones, A. G. and Elson, T. P., “Flow Dynamics in a Draft-Tube Bubble Column Using Various Liquids,” Chem. Eng.Sci., 46(2), 657-663(1991).
23. Hatch, R. T., “Experimental and Theoretical Studies of Oxygen Transfer in the Airlift Fermenter,” Ph.D. Thesis, MIT(1973).
24. Perry, R. H. and Green, D. W., (Ed.) Perry’s Chemical Engineers' Handbook, 7th ed., McGraw-Hill, New York(1997).
25. Choi K. H., “Prediction of Gas Holdup in Various Types of Airlift Reactors,” Korean J. Chem. Eng., 38(9), 1781-1790(2021).