Mixing characteristics in jet bubbling reactor

doi:10.11949/j.issn.0438-1157.20150435

Abstract

Abstract:

The jet bubbling reactor uses liquid jet to achieve the liquid mixing instead of mechanical stirring, which brings several advantages such as simple structure and low cost of maintenance and manufacturing. The research of its mixing characteristics plays a significant role in the design, optimization and scaling up of the reactor. Based on the air-water system, the electrolyte tracer (KCl solution) method was applied to investigate the influences of gas velocity and jet Reynolds number on the liquid mixing time with the cold model experimental apparatus. The mixing mechanism in jet bubbling reactor had also been analyzed from the perspective of power input. The results showed that within the experimental range (u_g from 0.0006 to 0.0343 m·s^-1, Re_j from 1.75×10⁴ to 7.00×10⁴), the introduction of gas bubbling strengthened the liquid mixing conditions. With the increase of superficial gas velocity, the liquid mixing time decreased at first and then increased. When the gas or liquid power input kept constant, the mixing time decreased with the increase of the total power input. Through the regression analysis of all the experimental data, relationship between liquid mixing time, and liquid and gas power inputs had been built up. An empirical correlation was proposed, and the calculated value was fitted well with the experimental data. Based on the obtained equation, the liquid mixing time was found to decrease at first and then increase with the increase of the gas power input if the total power input was remained constant. The transition point was around where gas input power occupied 61% of the total input power. At this point, the synergistic effect was the strongest.

Key words: multi-phase reactor, mixing, bubble, jet, power input

摘要：

射流鼓泡反应器以液体射流代替搅拌实现液相混合,具有结构简单、制造及维护费用低等诸多优点,研究其混合特性对于反应器的设计、优化及放大具有重要意义。以空气-水作为模拟介质,采用KCl电解质溶液为示踪剂考察了表观气速和射流Reynolds数的大小对液相宏观混合时间的影响,并从能量输入的角度对射流鼓泡反应器的混合机制进行分析。研究发现,在实验条件下(表观气速变化范围为0.0006～0.0343 m·s^-1,射流Reynolds数的变化范围为1.75×10⁴～7.00×10⁴),鼓泡的加入使得均相射流反应器内的液相混合得到改善;随着表观气速增大,液相宏观混合时间先缩短后延长;当气体输入功率或液体输入功率不变时,混合时间随总输入功率的增大而缩短。通过对多组实验数据的回归分析,提出了液相宏观混合时间与液体输入功率和气体输入功率的经验关联式,计算值与实际值吻合较好。最后基于提出的关联式,发现当总输入功率一定时,混合时间随气体输入功率的增加先缩短后延长,临界转变点在气体输入功率为总功率的61%处,此时气液两相协同作用最强。

关键词: 多相反应器, 混合, 气泡, 射流, 输入功率

CLC Number:

TQ027.1

GUO Tianqi, HUANG Zhengliang, WANG Jingdai, JIANG Binbo, YANG Yongrong. Mixing characteristics in jet bubbling reactor[J]. CIESC Journal, 2015, 66(11): 4438-4445.

郭天琪, 黄正梁, 王靖岱, 蒋斌波, 阳永荣. 射流鼓泡反应器的混合特性[J]. 化工学报, 2015, 66(11): 4438-4445.

References 21

[1]	Meng Huibo(孟辉波), Wang Yanfen(王艳芬), Yu Yanfang(禹言芳), Wang Wei(王伟), Wang Feng(王丰), Wu Jianhua(吴剑华). Research progress of mixing time in jet mixing equipment [J]. Chemical Industry and Engineering Process(化工进展), 2012, 31 (12): 2615-2625.
[2]	Fossett H, Prosser L E. The application of free jets to the mixing of fluids in bulk [J]. Proceedings of the Institution of Mechanical Engineers, 1949, 160 (1): 224-232.
[3]	Fox E A , Gex V E. Single-phase blending of liquids[J]. AIChE Journal, 1956, 2 (4): 539-544.
[4]	Lane A G C, Rice P. Comparative assessment of the performance of the three designs for liquid jet mixing [J]. Industrial & Engineering Chemistry Process Design and Development, 1982, 21 (4): 650-653.
[5]	Simon M, Fonade C. Experimental study of mixing performances using steady and unsteady jets [J]. The Canadian Journal of Chemical Engineering, 1993, 71 (4): 507-513.
[6]	Brooker L. Mixing with the jet set [J]. Chemical Engineer-London, 1993, (550): 16.
[7]	Ranade V V. Towards better mixing protocols by designing spatially periodic flows: the case of a jet mixer [J]. Chemical Engineering Science, 1996, 51 (11): 2637-2642.
[8]	Giorges A T, Forney L J, Wang X. Numerical study of multi-jet mixing [J]. Chemical Engineering Research and Design, 2001, 79 (5): 515-522.
[9]	Jayanti S. Hydrodynamics of jet mixing in vessels [J]. Chemical Engineering Science, 2001, 56 (1): 193-210.
[10]	Rahimi M, Parvareh A. Experimental and CFD investigation on mixing by a jet in a semi-industrial stirred tank [J]. Chemical Engineering Journal, 2005, 115 (1/2): 85-92.
[11]	Evans G M. A study of a plunging jet bubble column[D]. New Castle: University of Newcastle, 1990.
[12]	Blenke H. Biochemical loop reactors [J]. Biotechnology, 1985, 2: 465-517.
[13]	Evans G M, Jameson G J. Hydrodynamics of a plunging liquid jet bubble-column [J]. Chemical Engineering Research and Design, 1995, 73(6): 679-684.
[14]	Amiri T Y, Moghaddas J S, Moghaddas Y. A jet mixing study in two phase gas-liquid systems [J]. Chemical Engineering Research and Design, 2011, 89(3A): 352-366.
[15]	Paul E L, Atiemo-Obeng V, Kresta S M. Handbook of Industrial Mixing: Science and Practice[M]. New York: John Wiley & Sons, 2004.
[16]	Zlokarnik M. Stirring[M]. Wiley Online Library, 1988.
[17]	Ma Yuelong(马跃龙), Huang Juan(黄娟), Shen Chunyin(沈春银), Dai Gance(戴干策). Liquid phase mixing time in bubble columns [J]. Journal of East China University of Science and Technology(华东理工大学学报), 2010, 36 (2): 165-172.
[18]	Tian Yanli(田艳丽).Numerical simulation on flow field of rotory jet mixing system and nozzle structure optimization[D]. Hangzhou: Zhejiang University, 2008.
[19]	Miron A S, Garcia M C C, Camacho F G, Grima E M, Chisti Y. Mixing in bubble column and airlift reactors [J]. Chemical Engineering Research and Design, 2004, 82 (10): 1367-1374.
[20]	Haque M W, Nigam K, Joshi J B. Optimum gas sparger design for bubble columns with a low height-to-diameter ratio [J]. Chemical Engineering Journal, 1986, 33(2): 63-69.
[21]	Zhang Yuanxing(张元兴), Xu Xueshu(许学书). Biochemical Reactor Engineering(生物反应器工程)[M]. Shanghai: East China University of Science and Technology Press, 2001.