مقایسه عملکرد راکتورهای ایرلیفت جریان داخلی و خارجی جهت تصفیه آب به کمک لجن فعال
محورهای موضوعی : آلودگی محیط زیست (آب و فاضلاب)محمد علی صالحی 1 , نسرین حکیم قیاسی 2
1 - استادیار مهندسی شیمی، گروه مهندسی شیمی، دانشکده فنی مهندسی، دانشگاه گیلان، رشت، ایران *(مسوول مکاتبات)
2 - کارشناسی ارشد مهندسی شیمی، گروه مهندسی شیمی، دانشکده فنی مهندسی، دانشگاه گیلان، رشت، ایران
کلید واژه: راکتور ایرلیفت, انتقال جرم, نگهداشت گاز, سرعت حجمی گاز,
چکیده مقاله :
زمینه و هدف: در این تحقیق اثر شرایط عملیاتی و پارامترهای طراحی مانند شدت هوادهی، نسبت سطح ناودان به بالارونده و خصوصیات مایع بر هیدرودینامیک و ضریب حجمی انتقال جرم در راکتور های ایرلیفت سه فازی بررسی شده است. روش بررسی: . آزمایش‌ها در راکتور ایرلیفت دارای حلقه خارجی با نسبت سطح ناودان به بالارونده 14/0 و راکتور های ایرلیفت داخلی با نسبت سطح ناودان به بالارونده36/0 و 1 انجام شده است. هوا و آب به ترتیب به عنوان فاز گاز ومایع و و لجن فعال به عنوان فاز جامد استفاده شده اند. یافته ها: نتایج نشان داد سرعت چرخش مایع، نگهداشت گاز و ضریب حجمی انتقال جرم با افزایش سرعت حجمی گاز، کاهش غلظت لجن و کاهش نسبت سطح ناودان به بالا رونده، افزایش یافته است. بیش‌ترین مقدار نگهداشت گازبرابر با 178/0 در راکتور ایرلیفت دارای حلقه خارجی با غلظت 1% وزنی لجن فعال در سرعت حجمی گاز 24/0 متر بر ثانیه مشاهده شد. مدلی برای پیش بینی اثر غلظت لجن فعال، سرعت حجمی گاز و نسب سطح ناودان به بالارونده بر انتقال جرم راکتور های ایرلیفت لجن فعال ارائه شده است که با نتایج تجربی تطابق خوبی دارند. بحث و نتیجه گیری: به‌طورکلی بررسی عملکرد راکتورهای ایرلیفت داخلی و راکتورهای ایرلیفت دارای حلقه خارجی در شرایط مختلف غلظت و سرعت حجمی نشان داد راکتور ایرلیفت دارای حلقه خارجی دارای عملکردی بهتر در مقایسه با راکتور ایرلیفت داخلی است.
Background and Objective: In This study the impacts of operating conditions such as aeration rate, the downcomer-to-riser cross-sectional area ratio (Ad/Ar), and liquid phase properties on the hydrodynamics and volumetric mass transfer coefficient in three-phase airlift reactors was investigated. Method: Experiments were conducted in external loop air-lift reactor with downcomer to riser cross-sectional area ratio (AD/AR=0.14) and internal air-lift reactors with downcomer to riser cross-sectional area ratios 0.36 and 1. Air and Water were used as gas and liquid phases, respectively and activated sludge is used as the solid phase. Findings: The liquid circulation velocity, gas holdup and mass transfer coefficient increased with an increase in the superficial gas velocity, decrease the sludge concentration and decrease downcomer to riser cross-sectional area ratio. The maximum amount of gas hold up, 0.178 in external air-lift reactor with 1%(w/w) activated sludge in superficial gas velocity 0.24(m/s) was observed. A model to predict the effect of activated sludge concentration, the superficial gas velocity and the downcomer-to-riser cross-sectional area ratio on the mass transfer activated sludge airlift reactors provided which with the experimental results are in good agreement. Discussion and Conclusion: The evaluation of internal and external reactors performance at different concentration and superficial gas velocity show that the air-lift reactor with external loop has better performance in comparison with internal airlift reactors.
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- Krichnavaruk, S., and Pavasant, P., 2002, Analysis of gas–liquid mass transfer in an airlift contactor with perforated plates. Chemical Engineering Journal, 89: p. 203-211.
- Lu, W. J., Hwang, S. J., and Chang, C. M., 1995, Liquid velocity and gas holdup in three-phase internal loop airlift reactors with low-density particles. Chemical Engineering Science, 50: p. 1301-1310.
- Benyahia, F., and Jones, L., 1997, Scale effects on hydrodynamic and mass transfer characteristics of external loop airlift reactors. Journal Chemical Technology and Biotechnology, 69: p. 301-308.
- Pittoors, E., Guo, Y., and Van Hulle, S. W., 2014, Oxygen transfer model development based on activatedsludge and clean water in diffused aerated cylindrical tanks. Journal of Chemical Engineering, 243: p. 51-59.
- Yang, F., Bick, A., Shandalov, S., Brenner, A., and Oron, G., 2009, Yield stress and rheological characteristics of activated sludge in an airlift membrane bioreactor. Journal of Membrane Science, 334: p. 83-90.
- Petersen, E. E., and Margaritis, A., 2001, Hydrodynamic and mass transfer characteristics of three-phase gaslift bioreactor systems. Critical Reviews in Biotechnology, 21: p. 233-294.
- Siegel, M. H. H., Herskowitz, M., and Merchuk, M., 1989, Hydrodynamics and mass transfer in a three-phase air lift reactor. Advances in Biotechnology Process. p. 337-351.
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- Chisti, M., & Moo-Young, M., 1987, Airlift reactors: characteristics, applications and design considerations. Chemical Engineering Communication,. 60: p. 195-242.
- Bentifraouine, C., Xuereb, C., and Riba, J. P., 1997, An experimental study of the hydrodynamic characteristics of external loop airlift contactors. Journal of Chemical Technology and Biotechnology, 69: p. 345-349.
- Malfait, J., Wilcox, D., Mercer, D., and Barker, L., 1981, Cultivation of a filamentous mold in a glass pilot‐scale airlift fermentor. Biotechnology and Bioengineering, 23: p. 863-877.
- Schlüter, S., Steiff, A., and Weinspach, P.M., 1995, Heat transfer in two-and three-phase bubble column reactors with internals. Chemical Engineering and Processing: Process Intensification, 34: p. 157-172.
- Merchuk, J. C., and Gluz, M., 1996, Airlift Reactors, in the encyclopedia of bioprocess technology, 38-54.
- Jin, J. V. L. B., Doelle, H., and Yu., Q., 1999, The influence of geometry on hydrodynamic and mass transfer characteristics in an external airlift reactor for the cultivation of filamentous fungi. World Journal of Microbiology and Biotechnology, 15(1): p. 73–79.
- Nikakhtari, H., and Hill, G. A., 2005, Hydrodynamic and oxygen mass transfer in an external loop airlift bioreactor with a packed bed. Biochemical Engineering Journal, 27: p. 138-145.
- Yang, F., Bick, A., Shandalov, S., Brenner, A., and Oron, G., 2009, Yield stress and rheological characteristics of activated sludge in an airlift membrane bioreactor. Journal of Membrane Science, 334: p. 83-90. Persian
- Al Taweel, A., Idhbeaa, A., and Ghanem, A., 2013, Effect of electrolytes on interphase mass transfer in microbubble-sparged airlift reactors. Chemical Engineering Science, 100: p. 474-485.
- Jin, B., Yin, P., and Lant, P., 2006, Hydrodynamics and mass transfer coefficient in three-phase air-lift reactors containing activated sludge. Chemical Engineering and Processing: Process Intensification, 45: p. 608-617.
- Kilonzo, P. M., Margaritis, A., Bergougnou, M., Yu, J., and Ye, Q., 2007, Effects of geometrical design on hydrodynamic and mass transfer characteristics of a rectangular-column airlift bioreactor. Biochemical Engineering Journal, 34: p. 279-288.
- Krichnavaruk, S., and Pavasant, P., 2002, Analysis of gas–liquid mass transfer in an airlift contactor with perforated plates. Chemical Engineering Journal, 89: p. 203-211.
- Lu, W. J., Hwang, S. J., and Chang, C. M., 1995, Liquid velocity and gas holdup in three-phase internal loop airlift reactors with low-density particles. Chemical Engineering Science, 50: p. 1301-1310.
- Benyahia, F., and Jones, L., 1997, Scale effects on hydrodynamic and mass transfer characteristics of external loop airlift reactors. Journal Chemical Technology and Biotechnology, 69: p. 301-308.
- Pittoors, E., Guo, Y., and Van Hulle, S. W., 2014, Oxygen transfer model development based on activatedsludge and clean water in diffused aerated cylindrical tanks. Journal of Chemical Engineering, 243: p. 51-59.
- Yang, F., Bick, A., Shandalov, S., Brenner, A., and Oron, G., 2009, Yield stress and rheological characteristics of activated sludge in an airlift membrane bioreactor. Journal of Membrane Science, 334: p. 83-90.
- Petersen, E. E., and Margaritis, A., 2001, Hydrodynamic and mass transfer characteristics of three-phase gaslift bioreactor systems. Critical Reviews in Biotechnology, 21: p. 233-294.
- Siegel, M. H. H., Herskowitz, M., and Merchuk, M., 1989, Hydrodynamics and mass transfer in a three-phase air lift reactor. Advances in Biotechnology Process. p. 337-351.
